London: Whatever else happens to Jack Sock at the ATP Finals this week, his between-the-legs volley at 4-4 in the second set of his debut match will feature in the end-of-tournament showreel.
Trouble is Roger Federer was on the other side of the net and Sock's magic moment proved in vain as the Swiss maestro spun a backhand winner past the stranded American.
Sock, the first American to qualify for the ATP Finals since 2011, felt Federer's winner owed a little to luck -- not that the world number two needed much of that commodity to claim his 53rd career victory in the season-ender.
"It was a minor shank. I don't know, it's Roger I guess. He can do no wrong. Everything goes in," Sock, who pushed the 36-year-old hard in a 6-4 7-6(4) defeat having dropped serve in the opening game, told reporters.
It was a fairly accurate description of Federer's astonishing year in which, after a six-month lay-off at the end of 2016, he returned to win the Australian Open and Wimbledon to reach 19 grand slam titles.
His seven titles so far this season is his best return since he won eight in 2007 and few would bet against him matching that by winning the a first ATP Finals title since 2011.
Not everything Federer hit went in on Sunday.
The world number two, who warmed up for London by donning a kilt in an exhibition match against Andy Murray on Tuesday, was not at his clinical best.
Two stunning backhands in the opening game of the match in a packed O2 Stadium earned him the only break in a match in which Sock, and his atomic forehand, was always a threat.
Federer, the oldest player to qualif6y for the ATP Finals since 1970, looked aghast as two break points went begging at 3-3 and another two at 4-4 in the second set.
Further stoic resistance by Sock saw him fend off more danger at 5-5 but Federer's serve was Swiss timing personified -- winning 29 of 32 points on his delivery in the second set.
Federer jumped into a 4-2 lead in the tiebreak and although Sock finally took a point off the six-time champion's serve to level at 4-4, Federer won the next three points.
"I had a tactical plan with my team. But very often in a first match like this, it gets thrown overboard and you're just happy to be serving well," Federer, who has never lost a set to Sock in four meetings, told reporters.
"Now I think I'm in the tournament. Just full steam ahead every match that comes."
Sock is one of four first-time qualifiers here, having gate-crashed the end-of-season party by winning the Paris Masters, from which Federer pulled out after suffering some aches and pains.
That decision meant Federer could no longer catch Rafael Nadal for the end-of-season number one spot for which he received his award on Sunday.
"He was better throughout the year. He played more tournaments. He was incredibly successful throughout," Federer said of the Spaniard who won the French Open and the U.S. Open having lost to Federer in an epic Melbourne final.
"I don't have any regrets because I feel like in my stage of my competition, my age, either it comes to me or it doesn't."
Later on Sunday German youngster Alexander Zverev makes his ATP Finals bow against Marin Cilic, while Nadal opens his round-robin campaign against David Goffin on Monday.