Defending champion Roger Federer maintained his perfect record at the Barclays ATP World Tour Finals this year with a 6-1 3-6 6-3 victory over Mardy Fish at the O2 Arena.
The world number four had already secured his place in the semi-finals with Tuesday's stunning win over Rafael Nadal, while Fish was playing purely for pride after two defeats.
It looked like being a very unhappy Thanksgiving for the American as Federer broke serve straight away and dominated the first set, but the second was a different story.
Fish, whose preparations for his first appearance at the end-of-season showpiece were hampered by a hamstring injury, took the fight to his opponent and began to have significant success, particularly on his forehand.
The 29-year-old broke for the first time in the fourth game and had chances in all Federer's service games, with the Swiss understandably not hitting the heights he found against Nadal.
In the end one break was enough, but Federer, who is looking for a record sixth title, upped the pace again at the start of the decider, and once he moved into a 3-0 lead there was no way back for Fish.
The victory was Federer's eighth in a row at the tournament after he went through last year's event unbeaten, while he also made it 15 successive victories since the US Open.