Juan Martin del Potro’s day ended far better than it started after he toppled world No1 Novak Djokovic in the opening round of the Olympic tennis tournament on Sunday night. Buoyed by a rollicking crowd and a reinvigorated forehand, the soft-spoken Argentine prevailed 7-6 (7-4), 7-6 (7-2) in a highly entertaining match of exquisite quality.

　　The rematch of the bronze medal match from four years ago – when Del Potro won in straight sets at the All England Club – had been scheduled for the early afternoon, but the freakishly high winds at midday caused a delay in the order of play. Those same winds had caused localized power cuts at the athletes’ village, which left Del Potro trapped in an elevator for 40 minutes.

　　But the atmosphere on the nearly-full 9,165-seat main show court at the Olympic Tennis Center was all the better under the lights as the well-lubricated audience chanted, sang, waved flags and cheered raucously between every point, leaving chair umpire Pascal Maria practically hoarse from calling for order.

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　　The 6ft 6in Argentinian once put forth as the future of the sport after subduing an imperial-era Roger Federer in the 2009 US Open final is down to No145 in the world after a litany of wrist ailments, comebacks and false starts that threatened his career.

　　But he defeated No4 Stan Wawrinka at Wimbledon in June despite entering the tournament having played only four grand slam matches since 2013, none since the Australian Open two years ago. And now Sunday’s emotional win, which although decided in a best-of-three-sets format unlike the grand slams, will no doubt bolster his confidence ahead of this month’s US Open in Flushing Meadows – to say nothing of this week.

　　Del Potro took the early edge in a first-set tiebreak, pounding a forehand into the corner to take the opener in 51 minutes. He’d already crushed 20 winners by then – twice Djokovic’s 10 – including 15 off a forehand that at times seemed to approach pre-injury vintage.

　　The 27-year-old was even better during the second set, when he hit 21 winners against only nine unforced errors and got the better of Djokovic on a series of electric baseline rallies.

　　Djokovic came within two points of defeat on several occasions when serving at 4-5 in the second, the Serb fought back to level the set and eventually force another tiebreaker. But Del Potro rattled off the first five points – including a weapons-grade forehand down the line on the third which brought the crowd to their feet – and led 5-1 going into the changeover.

　　Moments later Del Potro ripped a cross-court forehand on match point that clipped the net and bounced inside the line to give him the victory after 2hr 27min. As the crowd erupted around them, the players shared an extended embrace at the net and parted misty-eyed.

　　The upset leaves Jo-Wilfried Tsonga as the top seed in the quarter, with Del Potro advancing to face Portugal’s João Sousa in the second round on Tuesday.