The Swiss world number two, bidding for a seventh title at the end-of-season finale, dished out yet more punishment to Ferrer in a 6-4 7-6 victory at the O2, taking his career record over the tenacious Spaniard to 14-0.
Federer took a while to settle into his smooth rhythm, though, and Ferrer, who beat Juan Martin del Potro in his opening match, had numerous opportunities in the opening games of their Group B clash.
Ferrer was 40-0 up on Federer's opening service game but having failed to capitalise he was immediately broken himself.
At 0-3 world number five Ferrer could have been forgiven for feeling pessimistic about his prospects but he was rewarded for his endeavour with a break in the fifth game when Federer wafted a backhand wide.
Having hauled himself back into the match Ferrer wavered at 5-6, however, allowing Federer to take the opening set.
Ferrer, darting around the court in his fluorescent lime green top, hung on to Federer's coat tails in the second set to extend the Swiss maestro into a tiebreak.
Even when Federer moved 6-3 ahead, Ferrer refused to accept the seemingly inevitable, saving two match points but there was no escape as Federer clinched his place in the semi-finals with one round-robin match to spare.
Ferrer's fate will be decided in the final round of group matches on Saturday when he faces Janko Tipsarevic.
Federer has now won his last 12 matches at the ATP World Tour Finals since losing to Nikolay Davydenko in the semi-finals when the tournament made its debut at the spectacular O2 Arena.
With two comfortable wins under his belt this year few would bet against him finishing his year on a high by clinching a hat-trick of titles here.
In the later Group B match, Tipsarevic faces Del Potro with both players seeking a first win.
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