Roger Federer overcame a stern test from Alexander Zverev to progress to the semi-finals of the ATP Finals with a three-set win on Tuesday.
With Jack Sock having beaten Marin Cilic earlier in the day, the Australian Open and Wimbledon champion knew he would clinch a place in the last four with victory,
Zverev has charged sharply up the rankings and now sits at third in the world, and the 20-year-old's contest with the 19-time grand slam winner was billed as a battle between the master and the apprentice.
It was the master who prevailed on this occasion, but only after he had received a significant examination from the German in what was the fifth match out of six at the season-ending showpiece to go the distance, with Federer eventually prevailing 7-6 (8-6) 5-7 6-1.
Zverev now must win his final clash in Group Boris Becker with Sock to seal his spot in the last four.
If an illustration of the challenge Zverev presents was needed, it was provided when Federer was forced to save three break points in the opening game, the Swiss then seeing one go begging in the subsequent game.
The fact that an exasperated Federer shouted, 'Come on!' as early as the fifth game after winning a point to go 40-30 ahead was a further compliment to Zverev, who summoned his resolve to withstand a late barrage, saving two set points in his last service game to force a tie-break.
He then raced into a 4-0 lead in the breaker, only for Federer to rattle off eight of the next 10 points - saving a set point in the process - to forge ahead.
Federer hit 17 winners to his opponent's 10 in the first set and it looked as if he would canter to a routine victory when he broke in the first game of the second courtesy of a lifeless Zverev drop shot before holding to love.
But again Zverev's admirable resilience came to the fore, a poor Federer volley giving him enough room to nail a forehand down the line and get the set back on serve.
Some strong serving and a deft backhand volley stopped Zverev from claiming the double break at 4-3 up, but Federer's backhand escaped him in the final game of the set.
Zverev surged into a 40-0 lead and, after seeing two break points squandered, clinched the third when Federer sent a cross-court shot wide at the end of a superb rally.
However, an errant cross-court backhand from the 20-year-old gave Federer the initiative and a 2-1 lead in the third, and this time there was no way back.
The double break came in short order as Zverev's forehand fell apart in the fifth game and, though Federer's serve came under some pressure in the next, he made no mistake in progressing to the semis for the 14th time in 15 tournament appearances.
Federer  bt Zverev  7-6 (8-6) 5-7 6-1
Federer – 26/38
Zverev – 20/45
BREAK POINTS WON
Federer – 4/8
Zverev – 2/11
FIRST SERVE PERCENTAGE
Federer - 53
Zverev - 63
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Federer - 83/54
Zverev - 73/43
Federer - 109
Zverev - 96
|James leaving Madrid was the best thing, says father|
|He´s looking good – Zidane thrilled with Ronaldo|
|It needs to take 30 seconds – Matic wants quicker VAR|
|Team LeBron edges Team Stephen in thrilling All-Star Game|
|McIlroy sees progress despite failing to contend at Riviera|
|Silver supports NBA players speaking out on social issues|
|Mickelson ready for Masters after third straight top-six finish|
|Gattuso: My job is to be the players´ nightmare until season´s end|
|I wasn´t good enough – Guardiola reveals Wigan rejection|
|Dillon reigns supreme with overtime win at Daytona 500|
|Bubba Watson ends drought with third Genesis Open title|
|Brazilian derby between Vitoria and Bahia abandoned after red-card frenzy|
|Anderson ends barren spell with New York Open triumph|
|It was crazy, but I like that - Zidane revels in eight-goal Betis thriller|
|Asensio credits Zidane for Madrid´s thrilling Betis comeback|
|Zidane hopeful over Marcelo hamstring injury|
|Overton replaces injured Plunkett for Blacks Caps ODI series|
|Bonaventura claims Milan can catch Inter|
|Bravo for Claudio! Guardiola to pick keeper at Wembley|
|Mourinho hoping for reinforcements at Sevilla|
|´Quick-healer´ Groves hopeful over shoulder injury|
|Real Madrid become first side to score 6,000 goals in LaLiga|
|Real Betis 3 Real Madrid 5: Asensio at the double in LaLiga classic|
|AC Milan 1 Sampdoria 0: Bonaventura makes it 10 unbeaten for Rossoneri|
|Schurrle excited to finally link up with Reus and Gotze|
|Fit-again Hughes included in England squad|
|New number one Federer revels in ´unbelievable´ week|
|Real Madrid defender Marcelo suffers hamstring injury|
|Costa fumes referees ´want to give me a card´, but Simeone plays down penalty row|
|Thiem regains Argentina Open title|
|Stoger makes Dortmund history with Gladbach win|
|Championship Review: Leeds fight back for point, Norwich & Ipswich share derby spoils|
|Racing beat La Rochelle to go second, Castres edge out Bordeaux|
|Borussia Monchengladbach 0 Borussia Dortmund 1: Burki unbeatable as Reus returns to haunt Foals|
|FA Cup ´magic´ no surprise to Pochettino after Rochdale thriller|
|Rochdale hero Davies: This is every kid´s dream|
|Atletico Madrid will not stop in pursuit of Barcelona, promises Gameiro|
|Banks boot pays dividends for Treviso|
|Lucky 13 and second successive title for Kvitova after Muguruza classic|
|´Wrong image´ to blame for VAR confusion in Manchester United´s FA Cup win|
|Rochdale 2 Tottenham 2: Davies denies Kane in FA Cup classic|
|Rieder stretchered off as Wasps extend Chiefs´ slump|
|Atletico Madrid 2 Athletic Bilbao 0: Gameiro and Costa settle cagey clash|
|NHL commissioner Bettman condemns ´reprehensible´ Smith-Pelly abuse|
|Visser, Scott and Nel among six recalled by Scotland|
|Bhuvneshwar and Dhawan inspire India´s Wanderers win|
|Napoli set club record with another Serie A win|
|Froome disappoints in time trial as Wellens wins Ruta del Sol|
|Napoli 1 SPAL 0: Allan sends hosts top of Serie A again|
|Federer makes short work of disappointing Dimitrov|
|Allegri allays Higuain injury fears|
|Blackhawks fans ejected after racist heckling of Capitals´ Smith-Pelly|
|Allegri convinced Juve can get past Spurs|
|Sri Lanka sweep series after dominating Bangladesh|
|Everton fear ´long-term´ injury for Mangala|
|If it isn´t Madrid, it´s Paris - Hazard tires of speculation|
|Luiten claims Oman Open title|
|Torino 0 Juventus 1: Champions win derby but lose Higuain|
|Neymar exit made Barcelona stronger - Ter Stegen|
|Remove T20 cricket from international schedule - Bayliss|
|Injured Higuain forced off against Torino|
|Jesus confident of returning strong after knee injury|
|DeGale launches Twitter attack on beaten Eubank Jr|
|We had to change hotels – Ovrebo recalls fury after 2009 Chelsea-Barcelona semi-final|
|Spalletti: Inter board will decide my future|
|Munro blitz helps Black Caps progress despite defeat|
|Fabregas still wary of timeless Iniesta|
|Liverpool´s 30-goal hero Salah: There´s more to come|
|Valverde: Coutinho dropped for the good of Barcelona|
|Garcia floors Rios for ninth-round TKO|