Stan Wawrinka kept his hopes of making the ATP World Tour Finals last four alive with a 7-6 (7-3) 7-6 (7-3) victory over Marin Cilic, who consequently bowed out of the competition.
Wawrinka was beaten in straight sets by Kei Nishikori in his Group John McEnroe opener on Monday, while Cilic also went down to Andy Murray.
Victory for Cilic would have sent Murray into the semi-finals, but Wawrinka performed better at the crucial moments to boost his hopes of advancing ahead of his final round-robin match with the world number one.
After an even start to the match the Swiss was forced to stave off set point in game 10, backing himself with a powerful second serve before forcing a tie-break.
The US Open champion's powerful groundstrokes continued to cause Cilic problems, and a poor lob from the Croatian was smashed back beyond him as the roaring Swiss took control.
Cilic responded in the best possible way as he moved a break up in the first game of the second set, but after Wawrinka hit back he threw his racket to the ground in frustration.
Once again chances were at a premium, but the Swiss came out on top in the tie-break once again.
After building a two-point advantage by forcing Cilic into the net and following up with an excellent forehand, Wawrinka had his seventh straight victory over the Croatian wrapped up when his opponent's return found the net.
Wawrinka  bt Cilic  7-6 (7-3) 7-6 (7-3)
Wawrinka - 21/33
Cilic - 22/28
Wawrinka - 7
Cilic - 8
BREAK POINTS WON
Wawrinka - 1/2
Cilic - 1/5
FIRST SERVE PERCENTAGE
Wawrinka - 64
Cilic - 44
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Wawrinka - 80/68
Cilic - 86/56
Wawrinka - 83
Cilic - 74