Federer was already guaranteed top spot in his section by virtue of that Nadal near-whitewash and a rather less straightforward three-set victory over Jo-Wilfried Tsonga.
Conversely, Fish, not at his best this week after hamstring injuries ahead of the London finale, was already out of contention for the semi-finals after losing to both Nadalâ€”in a final set tie-breakerâ€”and to Tsongaâ€”losing a first-set tie-breaker on that occasion.
Whether it was because this was, in effect, a dead match, or that Federer had been keeping late hours the night before with his football mate, Thierry Henry, at Arsenalâ€™s Champions League match at the Emirates Stadium. Or perhaps it was simply that he had not expected such a good fight from this opponent.
But against the odds, this turned into closely fought roller-coaster of a match between the two oldest men in the competition that stretched over three sets and just 12 minutes short of two hours before Federer closed the deal, 6-1, 3-6, 6-3.
When he broke Fishâ€™s opening service game at the fourth attempt, it looked a case of same-old, same-old, but he was immediately broken back.
However, Federer stamped his authority on the set with two more breaks and resisted an assault from the Fish cross-court forehand that took him 0-40 down to serve out the set, 6-1.
But the second set was Fishâ€™s as he upped the tempo of his serve to 130mph plus and returned with ease the Federer wide-kicking serve that has so disrupted other players. He made 16 winners in the set while Federer hit error after errorâ€”11 in this set aloneâ€”and the American broke in the fourth game and served out the set confidently, 6-3.
In the third, apparently woken from his slumber, Federer took the attack to Fish. After a strong hold of serve, he began to rush the net and picked off volleys in style to force the break and lead 3-0.
Fish saved another break point to finally get a game on the board but picked up only four more points on Federer’s serve in the final set, a comfortable 6-3.
Federer admitted to struggling to find the intensity that he had shown against Nadal, but was quick to give credit to Fish.
â€œI definitely struggled a little bit more today, but I thought that was more due to the circumstances and Mardy actually playing well for most of the match.
â€œHeâ€™s always very dangerous, takes the ball extremely early, serves great and can get on a roll. I was worried in the third set. I thought I was going to lose today but Iâ€™m very happy. Itâ€™s been a great run since the US Openâ€”I’ve been all round the world but Iâ€™m still going strong. Hopefully I can make it a nice weekend.â€
He was referring, of course, to his attempt, come Saturday and Sunday, to win a record sixth season-end title. And as this was his 37th career victory in the competition, he can also equal Ivan Lendlâ€™s current record of 39 should he win that record final.
Federer is now on a 15-match streak and remains unbeaten indoors since the US Open following back-to-back titles in Basel and Paris. It looks as though only the best of tennis can derail the Swiss No4â€™s ambitionâ€”and that ambition may include his return to No3 before Christmas: He can overtake Andy Murray if he reaches the final.
He asserted, none the less, that that was the last thing on his mind. â€œItâ€™s not going to change anything for the seedings at the Australian Open, so for that reason, it doesnâ€™t change anything for me.â€
For a taste of Federer in action as he progressed, unbeaten, to the WTF semi-finals, check out this on-the-scene selection.
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BIOGRAPHY: Ethan Hazard
BIOGRAPHY: Daniel Sturridge