Davis Cup action continues this weekend with four World Group quarter-final ties. World No. 2 Novak Djokovic looks to continue his Davis Cup success, while Belgium continues their quest for a first title.

SERBIA vs. SPAIN 

Aleksandar Nikolic Arena, Belgrade, Serbia (Indoor Hard)

After a right elbow injury forced him to withdraw from Miami, Djokovic has declared himself fit and ready to go for this tie against Spain. He and Viktor Troicki will have their work cut out for them against a tough Spanish squad led by Pablo Carreno Busta and Albert Ramos-Vinolas.

Djokovic has not dropped a set in his FedEx ATP Head2Head rivalries against Carreno Busta (1-0) and Ramos-Vinolas (2-0). However, Ramos-Vinolas lead his FedEx ATP Head2Head with Troicki 2-0.

Spain defeated Serbia in their only previous Davis Cup meeting, a 4-1 first-round win in 2009. The Spanish squad went on to win the title that year.

AUSTRALIA vs. UNITED STATES

Pat Rafter Arena, Brisbane, Australia (Outdoor Hard)

One of the most celebrated Davis Cup rivalries will be renewed when Australia and the United States square off once again in Brisbane. Team USA leads the Davis Cup head-to-head 26-20 and prevailed at this very juncture last year, scoring a 3-1 quarter-final win on a grass court in Melbourne.

Perhaps the most anticipated match of the tie is the fourth rubber between Nick Kyrgios and Jack Sock, which marks their first-ever FedEx ATP Head2Head meeting. Isner leads the FedEx ATP Head2Head rivalry with Kyrgios 2-1, but the Aussie won their most recent meeting this past July in the Atlanta final.

The United States squad will have the luxury of making quality substitutions to their singles lineup if needed, with Steve Johnson and Sam Querrey, both inside the Top 30 of the Emirates ATP Rankings, rounding out their team.

BELGIUM vs. ITALY

Spiroudome de Charleroi, Charleroi, Belgium (Indoor Hard)

2015 Davis Cup finalists Belgium will have the home crowd on their side as they face a veteran Italian team. Italy leads 5-3 in their Davis Cup head-to-head against Belgium, but lost their most recent meeting in 2000.

The Belgian team will be led by experienced Davis Cuppers David Goffin and Steve Darcis, while Italy will have Paolo Lorenzi and Andreas Seppi flying the flag in singles.

Goffin leads his FedEx ATP Head2Head with Seppi 2-0, with both wins coming in 2015. Darcis is even in his FedEx ATP Head2Head with Seppi at 1-1, but won their most recent match this February in Sofia. He trails Lorenzi 0-1 in their FedEx ATP Head2Head.

FRANCE vs. GREAT BRITAIN

Kindarena, Rouen, France (Indoor Clay)

The French squad is hopeful that slow clay will blunt the power hitting from Team GB. The Brits lead their Davis Cup head-to-head 12-9 and won their most recent tie in 2015, a 3-1 quarter-final victory on grass in London.

Rising stars Kyle Edmund and Daniel Evans will lead the way in singles for Great Britain as they face World No. 17 Lucas Pouille and veteran Jeremy Chardy. Edmund defeated Pouille this January in Brisbane, but the remaining singles encounters will all be first-time FedEx ATP Head2Head meetings.

The doubles rubber could play a meaningful role in which team prevails, with Julien Benneteau and Nicolas Mahut squaring off against Dominic Inglot and Jamie Murray.

The season is only three months old but there’s already a plethora of storylines to track. Here are the top seven stories of 2017 so far:

1. Roger Federer’s Surprise Start

Federer, arguably the greatest player of all-time, has been the story of 2017. The Swiss star is still bringing his love for tennis that has helped millions of fans adore him. But Federer’s ability to change might be the most impressive detail about his comeback so far. The right-hander has surprised and impressed most with his new flattened-out backhand, aided by his bigger, 97-inch racquet.

Heck, the fact that Federer still wants to tinker with his game – at 35 years old, in his 20^th year on tour and with four kids and Mirka at home – is worth noting as well.

No one expected Federer to sprint to a 19-1 start and to beat Rafael Nadal three times, including during two finals – Australian Open and the Miami Open presented by Itau – and no one knows what the remainder of 2017 will hold for the 26-time ATP World Tour Masters 1000 champion. Maybe No. 1 in the Emirates ATP Rankings?

Federer’s Best Starts To A Season

2. Rafael Nadal’s Resurgence

Two of the biggest questions coming into 2017: How would Federer come back, and how would Nadal return after another injury? We know about Federer, and we now know about Nadal as well. The Spaniard has hit top form on the hard courts, reaching three finals – Australian Open (l. to Federer), Abierto Mexicano Telcel (l. to Querrey) and the Miami Open presented by Itau (l. to Federer) – and has posted a 19-4 record to start 2017, tying him with Federer for the most wins to date.

Perhaps most importantly, Nadal feels good about his team’s new addition, Carlos Moya, and about his play. “I am at a very high level of tennis and I believe I am ready to win titles,” Nadal said after falling in the Miami final. “I’m playing well [enough] to fight for everything.”

With the clay-court season set to start next week, expect Nadal to be feeling even better about his tennis.

FedEx ATP Win/Loss Index (2017)

3. Nick Kyrgios’ Play

His start to the year was hardly what he had imagined: a five-set loss to Andreas Seppi in the second round of his home Grand Slam. But Kyrgios has answered nearly every question that trailed him in Melbourne.

Mental toughness? See back-to-back straight-set wins against Novak Djokovic in Acapulco and Indian Wells. Showing up at every event? His last four tournaments: semi-final in Marseille; semi-final in Acapulco; quarter-final in Indian Wells; and semi-final in Miami.

His attitude? “I feel like my level of tennis, it’s always been high, but mentally I’m competing for every point. That’s making the difference,” he said after his Miami semi-final loss to Federer, one of the best matches of 2017. “I got a lot of work to do. I’m 16 in the world. There are 15 players better than me.”

4. Jack Sock Climbing The Emirates ATP Rankings

The Nebraska native has more than carried the American flag for the first three months of the season. After not winning a title during all of 2016, Sock has already captured two crowns – Auckland and Delray Beach. At the March Masters, he made his first Masters 1000 semi-final in Indian Wells (l. to Federer) and backed it up with a last-eight showing in Miami (l. to Nadal).

Sock is 18-4 on the season, second behind only Federer and Nadal in wins. The Kansas City resident reached a new career high of No. 15 in the Emirates ATP Rankings this week. At this rate, the 24 year old will crack the Top 10 by the end of the season and become the first American to do so since John Isner in May 2014. Sock is currently No. 7 in the Emirates ATP Race To London.

5. Alexander Zverev Leading #NextGenATP

#NextGenATP players continued to make strides during the first few months of 2017. Russian Daniil Medvedev celebrated his first final at the Aircel Chennai Open (l. to Bautista Agut). Emirates ATP Star Of Tomorrow Taylor Fritz checked off his first Top 10 win by beating Marin Cilic in Indian Wells. But no #NextGenATP player has delivered like Zverev this season.

The 19 year old won his second ATP World Tour title at the Open Sud de France in Montpellier. In Miami, he improved to 2-0 against Stan Wawrinka in their FedEx ATP Head2Head rivalry and made his first Masters 1000 quarter-final (l. to Kyrgios). The strong start has Zverev atop the Emirates ATP Race To Milan, which will determine who qualifies for the inaugural Next Gen ATP Finals, to be held 7-11 November in Milan.

6. Grigor Dimitrov Knocking On Top 10

The Bulgarian already has two titles – Brisbane and Sofia – and returned to the semi-finals of a Grand Slam for the first time since 2014 Wimbledon. Before falling to Nadal in the Australian Open semi-finals, Dimitrov had won 10 consecutive matches. He’s 3-1 against Top 10 players and he might be rejoining that elite group soon.

Dimitrov is currently No. 12 in the Emirates ATP Rankings but he’s played like a Top 5 player so far this season. His spot in the Emirates ATP Race To London: No. 4.

7. Surprise Beginnings From Andy Murray, Novak Djokovic

They’re ahead of Federer in the Emirates ATP Rankings, but No. 1 Murray and No. 2 Djokovic have garnered a small fraction of the attention that Federer has received so far. Djokovic started the year with a memorable run in Doha, beating Murray for the title in one of the best matches of the year. That epic final had tennis fans thinking that this year’s battle for No. 1 would again be a two-man affair.

But both Murray and Djokovic suffered early losses in Melbourne. Murray rebounded in Dubai to celebrate his 45^th tour-level title, while Djokovic fell to Kyrgios in the Acapulco quarter-finals. In Indian Wells, both fell before the last eight, and they both withdrew from Miami with elbow injuries. With three Masters 1000 tournaments only weeks away, though, both men will be looking to get their season back on track.

The first quarter of 2017 is in the books, so let’s see who had the hot hand to start the new year.

The big picture clearly shows Roger Federer and Rafael Nadal out in front in the Emirates ATP Race To London. But what about the specifics of serving, returning and elevating in the pressure moments? That’s where the specific metrics of our game step in to paint a clearer picture.

An Infosys ATP Beyond The Numbers analysis of the first quarter identifies four players who are outperforming their peers, laying the foundation for a rise up the Emirates ATP Rankings this season.

No. 1 Service Games Won = Nick Kyrgios 93.3% (208/223)

Ivo Karlovic has been the leader in this category for the past three years, but Kyrgios has knocked the 6’11” Croatian into second place to kick off 2017. Kyrgios defeated Karlovic 6-4, 6-7(4), 7-6(2) in the third round of the Miami Open presented by Itau last week.

Kyrgios broke Karlovic once in the opening set, while the Croatian was not able to break Kyrgios at all, seeing just one break point for the match. The Australian dropped serve twice in his opening-round match in Miami against Damir Dzumhur, and then only dropped serve once (to Federer) during the next 62 service games.

No. 1 Break Points Converted = Daniel Evans 53.7% (51/95)

Evans reached a career high of No. 41 just four weeks ago and currently sits at No. 44. He has a 10-6 record in 2017 after going 9-10 up to this point in 2016. Evans is taking advantage of the big moments so far this season.

He’s the only player on the ATP World Tour who has converted more than half of his break points. Evans reached the final of the Apia International Sydney in January, converting an impressive 64.5 per cent (20/31) of his break points.

No. 1 Break Points Saved = Grigor Dimitrov 75.9% (101/133)

Dimitrov has been one of the most dangerous players on tour in 2017, with two titles and a 17-4 record. He played what some think has been the highest quality match so far this season, narrowly going down to Rafael Nadal in five sets during the semi-finals of the Australian Open.

The Bulgarian saved 61.5 per cent (8/13) of his break points in that match, and is saving an astounding 75.9 per cent so far this season. Dimitrov is now up to No. 12 in the Emirates ATP Rankings, from No. 17 at the start of the year, and is knocking hard on the Top 10.

No. 1 Second-Serve Return Points Won = Richard Gasquet 61.1% (225/368)

The 30-year-old Frenchman had a solid February, reaching the final of the Open Sud de France in Montpellier and the semi-finals of the Open 13 Marseille. Gasquet’s career average for winning second-serve points is 51 per cent, so he is clearly crushing that at 61.1 per cent. To give some historical perspective, Spaniard Alberto Berasategui has the career record for second-serve points won at 56.3 per cent.

The very best parts of Roger Federer and Rafael Nadal’s FedEx ATP Head2Head rivalry will remain unquantifiable forever. How their games have evolved throughout their careers. The passion they share for tennis. The feelings of excitement they’ve provided millions of fans during the past two decades.

But certain aspects of their rivalry, one of the best in all of sport, can be counted. And when you’ve played each other 37 times over 14 years and your match-ups have decided 23 tour-level titles, the numbers add up quickly.

To begin: They’ve spent a lot of time together. Nadal and Federer have been on court together for the equivalent of almost four full days – three days, 17 hours and 16 minutes, to be precise. If you’re thinking about that in terms of a workweek, that’s one busy week – 89 hours.

They’ve played more than 7,000 points, more than 1,100 games and more than 100 sets. They’ve had their share of faults – 126 double faults to be more accurate – but they’ve also aced each other dozens of times, and that’s not hyperbole.

To relive all 37 matches they’ve played, click here. For more stats, keep reading.

By The Numbers: Federer v. Nadal