Italian wild card Gianluigi Quinzi must have felt like it was 2013 again. The former junior World No. 1, who won the 2013 Wimbledon boys junior title, was even with top seed Andrey Rublev for 90 minutes on Tuesday at the Next Gen ATP Finals.

The 21-year-old Quinzi had recovered from blowout sets, pushed through exhaustion and found a way to extend the favoured Rublev into a fifth set. But it was late in that decider when the 20-year-old Rublev, already an ATP World Tour titlist, focused on the end goal and sprinted to the finish.

The Russian won 11 of the final 14 points against the home favourite to avoid a stunning opening loss, beating Quinzi 1-4, 4-0, 4-3(3), 0-4, 4-3(3) to conclude Day 1 in Milan.

Rublev won his first title in July on the clay in Umag and has been one of the front-runners of the #NextGenATP group since his triumph. At the US Open, the right-hander beat Nitto ATP Finals qualifiers David Goffin and Grigor Dimitrov en route to becoming the youngest quarter-finalist in New York since Andy Roddick in 2001.

The 6’2” Russian reached another quarter-final in October at the China Open in Beijing. But he had trouble against Quinzi, who was playing with momentum and a home crowd.

The Italian had won three consecutive matches in the 21-and-under Italian Next Gen ATP Finals Qualifying tournament last weekend to make the Next Gen ATP Finals. And during the qualifying tournament, Quinzi had become accustomed to some of the new rules and innovations taking place this week in Milan, including the shorter format: first to four games sets and no ad scoring.

Quinzi darted to start the match, blanking Rublev in the opener. But the Italian felt fatigued in the second. During his conference with his coach after the second set, Quinzi said, “Physically, I’m dead.” Rublev also raised his level in the third, saving all three break points.

But Quinzi recovered well in the fourth before the Russian played his most consistent tennis late in the fifth set.

They say that one point could change a match. That rang plenty true in the third match of the inaugural Next Gen ATP Finals.

Borna Coric used a line-clipping return down set point in the first set to turn his opening match of the tournament around before ousting Jared Donaldson, 4-3(2), 4-1, 4-3(5), on Tuesday evening.

The American appeared to be control, having broken at 2-2 in the opener. But on a deciding-point deuce, the Croatian lunged out wide for a forehand, which he sent flying crosscourt off the edge of the line to save the set and with it, gain all the momentum he needed to storm away from his opponent.

As Coric’s coach said after his charge won the first-set tie-break — players are allowed to put on a headset to communicate with their coach after each set — it would be important to change directions on the backhand side. And Coric executed the advice to perfection, becoming more aggressive and controlling play with laser-like backhands down the line throughout the final two sets. Donaldson did not take advantage of the in-match coaching innovation in his opener.

One of the other innovations in Milan — a shorter set — made it tough for Donaldson to wrestle the momentum back to his side of the court. In short order, 20 minutes to be exact, Coric won the second set on the back of an immediate break of serve. And once the Croatian grabbed that lead, a comeback seemed daunting for the American.

Donaldson managed to force a tie-break in the third set. But when Coric hit a serve off the net at 6-5 that bounced in the box — there are no lets in Milan — his opponent had difficulty getting a racquet on the ball. Coric easily put the next shot away to move to 1-0 at the Fiera Milano.

The inaugural Next Gen ATP Finals has begun with an upset.

Seventh seed Daniil Medvedev of Russia came back from a set down on Tuesday afternoon to surge to the top of Group B, knocking out countryman Karen Khachanov 2-4, 4-3(6), 4-3(2), 4-2 at the Fiera Milano.

The all-Russian battle was dominated by Khachanov in the early goings, as the 6’6” Russian controlled play with his heavy forehand. But his 6’6” countryman Medvedev evened the contest in an entertaining and back-and-forth tie-break.

In the third and fourth sets, Medvedev pulled away as he kept Khachanov in the back of the court and frequently dictated play. The seventh-seeded Medvedev in particular used his backhand up the line well against his countryman.

The opening match of the tournament also featured many of the innovations that will be the hallmark of the event. Both players talked with their coaches through headsets at the end of the second and third sets. There were at least two let serves that were played.

Well, one was played. On the first let serve, chair umpire Carlos Bernardes, out of habit, said let and then called let again because the players are to play all serves that hit the net cords.

Khachanov is one of the favourites to do well in Milan. He leads the field with 25 wins this season and has been one of the leaders of the #NextGenATP field this season.

But he is only 6-19 on hard courts this year and will now look to climb out of a 0-1 hole at the Next Gen ATP Finals.

Medvedev has also been up and down in 2017, reaching six quarter-finals, a semi-final and his maiden final in Chennai, but also suffering losing streaks of six and eight. On Tuesday, though, he put it all together to become the first winner in Milan.

Chances are your “did-you-see-that?” moment came later in the set, when more was at stake and players had sharpened their play because of the scoreline.

The big moments – pick your favourite: break points, set points, tie-breaks – stick with us, for better or worse. So, if you could, why not try to create more of those moments?

That’s the reasoning behind one of the most noticeable innovations to be tested during the inaugural Next Gen ATP Finals, to be held 7-11 November.

Matches in Milan will use a shorter format: best-of-five set matches, but the sets will be first to four (with a tie-break at 3-3), and games will feature no-ad scoring.

“We’re looking to create more meaningful moments throughout the course of a tennis match. Normally you’d say break points, game points, latter stages of sets, tie-breaks would be more meaningful moments,” said Ross Hutchins, Chief Player Officer, ATP. “So can we host more tie-breaks, more end of sets, more exciting moments, more clutch points?”

Under the new format, the minimum numbers of games needed to win – 12 – is the same number a player needs to win during a best-of-three-sets match. But the shorter format could produce completely different matches, Hutchins said.

Momentum could change more often, with new sets possibly happening every five or six games. The scoreline of a close match could easily be 4-1, 1-4, 4-1, 2-4 as it heads into a fifth set.

Hutchins also predicts players will place more emphasis on the beginning of sets, because they know they have limited time to turn it around.

“One all is the equivalent of 3-all. When you start looking at 2-all, 2-all is 4-all, and you’re within two games of winning the set… All of sudden the start of a set is a lot nearer to the end of a set,” Hutchins said. “Players will realise it’s tougher to get back into the sets so they’ll put more work into holding serve or breaking serve.”

The deciding deuce point, a staple on the ATP World Tour doubles circuit, will feature an exciting new twist as well. In doubles, the receiving team gets to decide who returns. But in Milan, the server will choose.

“We know and have seen the deciding point receiver’s choice in doubles. But in keeping with the concept of the event, we thought it would be interesting to see how the server’s choice would be viewed and also the mindset of the players having to choose their service side,” Hutchins said.

Other innovations similarly take aim at creating more exciting moments for players and fans. Warm-up time before a match will be reduced to five minutes.

“Guys should be ready to go nearly as soon as they get out there,” said former World No. 1 Lleyton Hewitt.

Let calls will disappear. If the serve clips the tape and rolls over, it’s an in serve and a live ball.

“A let is sort of ‘Let’s go again’. Nothing really happens so it’s just a question of trying to create more excitement, and an additional element of unpredictability, within the matches,” Hutchins said.

Fans will get to experience more of these moments as well, as onlookers on the sides of the court will be allowed to move freely rather than waiting for changeovers to come back into the stadium. (Movement will remain restricted behind the baselines.)

“We’re trying to create less down moments and less pauses in play and less restriction from all stakeholders, whether it be the crowd, the media, the broadcaster, how we work,” Hutchins said.

The removal of let serves might have the biggest effect on players’ pre-tournament practices.

“I think all the rules they’ll have to practise, especially the lets. Players will be so used to stopping, they’ll immediately switch off. Actually, I think it will take a couple days to get used to this but that’s why it’s such a good time to host this event. It’s at the end of the year, with not much else going on. Depending on what they do during the Rolex Paris Masters, they’ll have a couple of days to practise,” Hutchins said.

#NextGenATP players also think the new rules will occupy some practice time.

“I think the hardest thing is going to be for the no lets. For the first couple of times I feel like I’m just going to stop the point and expect a re-serve,” said Canadian Denis Shapovalov.

Hutchins is aware of the potential drawbacks that could accompany the innovations, including the no-let rule. Say it’s match point, 3-2, 40/30 in the fifth set, and the serve clips the tape and trickles over the net. A let serve ace on match point could happen, he said, but you also could have a let winner two more shots into the point.

To Hutchins and others, the endless discussion about hypotheticals can wait for another day. In Milan, it will be time to abandon the theories and live in the reality.

Hutchins said, “We could all predict what could happen. We could all predict what could be but we don’t know. And that’s what this event is there to show; it’s to test things.”