It’s the hardest hit shot, and is the driving force behind the most common rally length in matches – a rally of just one shot. The serve went in, but the return didn’t come back in play. That rally length happens way more than anything else, right around 30 per cent of total points.

It creates the greatest paradox in our sport – the practice court is overflowing with forehands and backhands, but the rally length that dominates the match court contains only a serve and a return.

See Nadal’s serving patterns in the Infosys Serve & Return Tracker 

An Infosys ATP Beyond The Numbers analysis identifies that only 222 players since 1991 have been able to make their second serve an asset – winning a minimum of 50.1 per cent of second-serve points played.

It’s an astonishing metric since most of us hold the view that the serve in general is a dominant weapon. First serves definitely are, but second serves are absolutely not.

World No. 1 Rafael Nadal is widely recognised as a preeminent returner in our game. He is third best on tour since 1991 in return points won against first serves, and fourth best returning second serves.

But there is a serve category in which he is simply the best: Nadal is No. 1 in second-serve points won, at 57.2 per cent (13,485/23,590). The Top 10 career leaders in this category:

Career Leaders: Top 10 Second-Serve Points Won

When you search farther down the list, just below the 50 per cent win mark, there is an impressive array of players who attained a coveted Top 10 ranking but had a losing record with second-serve points won.

Top 10 Players: Career Second-Serve Points Won

Second serves are the real battleground in our sport. First-serve win percentage is always positive in our sport, all the way down to Under 12s. Not even close with second serves.

At last month’s Australian Open, Nadal averaged hitting his first serve 114 mph (180 km/h) through five matches to the quarter-finals. His average speed on second serves dropped to 95 mph (153 km/h).

That’s a 19 mph (31 km/h) difference, and is the primary reason winning points behind second serves becomes so much tougher. It’s simply not the big hammer like the first serve.

Juan Martin del Potro has undoubtedly been one of the hottest players on the ATP World Tour, breaking back into the Top 10 of the ATP Rankings in January for the first time since 4 August 2014. So it was no surprise to see Del Potro cruise to a 6-2, 6-4 victory against Frenchman Jeremy Chardy at the Delray Beach Open on Tuesday evening.

It could be the beginning of another big run in Florida for the 29-year-old, who has advanced to at least the semi-finals in each of his three previous appearances in Delray Beach. Del Potro claimed the title on his debut in 2011 (d. Tipsarevic). The World No. 10, who has now triumphed in the opening round of his past 23 events, has won at least two matches at his past six tour-level tournaments. 

The ‘Tower of Tandil’ will next face American Frances Tiafoe, who advanced on Monday. Del Potro leads the American — who has idolised the Argentine — 2-0 in their FedEx ATP Head2Head series.

While Del Potro advancing was no surprise, there was an upset elsewhere in the draw. American Taylor Fritz, who had not played a tour-level match in 2018, upset World No. 12 Sam Querrey 2-6, 6-3, 7-6(4) just two days after the fourth seed competed in the final of the inaugural New York Open (l. to Anderson).

“I didn’t even know it was my first tour-level match of the year,” Fritz said . “I felt ready. I did well in the Challengers I played this year… took last week off, was training hard, and I felt ready.”

The World No. 85 has shown good form, reaching the ATP Challenger Tour final in Noumea, New Caledonia before capturing the title in Newport Beach, California later in January.

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“I feel like I’m finally hitting my stride again after I had a good offseason,” Fritz said. “I feel like I’m still riding that wave of confidence from the success I was having at the Challengers and now this even solidifies the confidence that I’ve been having in myself and in my game.”

Another #NextGenATP star also impressed on Tuesday, as 2017 Next Gen ATP Finals qualifier Denis Shapovalov shrugged off an immediate break of serve to beat 38-year-old Ivo Karlovic 7-5, 7-6(4). 

“It was definitely difficult. Ivo’s been around for so many years. It’s never easy playing a giant like him,” Shapovalov said. “There’s no rhythm in the match.”

The Canadian faced a tough task when he was broken by Karlovic in his first service game of the match, especially since the Croatian showed good form by advancing to the quarter-finals at the New York Open last week. But despite facing an opponent who had held 97 per cent of his service games this year, Shapovalov stayed the course. The left-hander seized both of his break chances in the first set before going on to win the match in one hour, 54 minutes. 

“I felt a lot of pressure at the beginning of the match,” Shapovalov said. “I didn’t know what to expect against a guy like that, but I just kept fighting, kept trying to win my serve and hopefully break him and I was able to turn the match around.”

Did You Know?
Del Potro beat three current or former Top 10 players in the ATP Rankings to win the title in Delray Beach in 2011. He did not drop a set at the event.

Could a Gael Monfils match possibly end quietly? It looked that way as Horacio Zeballos led 5-2 in the third set of their first-round encounter at the Rio Open presented by Claro on Tuesday evening. The Frenchman even faced match point as the left-hander served for the match at 5-3.

But Monfils would find his entertaining best to win the final five games of the match to clinch a 7-5, 3-6, 7-5 victory against the Argentine.

The recent Qatar ExxonMobil Open champion, who also advanced to the semi-finals at the Argentina Open last week, is now five-for-five in opening-round matches this season. He continues his pursuit of a second title in 2018 — if he wins another trophy this year, it will be the first time Monfils has won multiple titles in an individual season.

But more immediately, ‘La Monf’ set up a blockbuster second-round battle against top seed and World No. 3 Marin Cilic, who advanced on Monday. Monfils has won both matches in their FedEx ATP Head2Head, including a meeting less than two years ago in Rio at the Olympics.

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Third seed Pablo Carreno Busta, who lost in his first match at his past two events (Quito, Buenos Aires), got back on track by defeating qualifier Marco Cecchinato 6-4, 6-1 in 64 minutes. That evens the Spaniard’s tour-level record for the year (4-4) as he attempts to defend finalist points from Rio de Janeiro last year (l. to Thiem).

Sixth seed Diego Schwartzman moved on when #NextGenATP Norwegian Casper Ruud retired down 1-4 in the opening set. The Argentine next plays someone who will certainly be riding high on confidence. 

His opponent, Federico Delbonis, captured his 100th tour-level win when Czech Jiri Vesely retired down 2-6, 2-3.

“It means a lot,” Delbonis said. “To have 100 match wins, it’s a big challenge and I’m so happy to reach it.”

Nine of the Argentine’s victories have been against opponents inside the Top 20 of the ATP Rankings. The left-hander is in-form, too, having made the semi-finals in Buenos Aires last week (l. to Bedene).