Roger Federer is (was?) so good that even when he loses, it's kind of like him winning. Since 1990, Federer has the worst record—4-24—in matches where the loser scores more points than the winner.
In a paper in International Journal of Performance Analysis in Sports looking at more than 61,000 ATP matches from 1990 to the present, researchers found that this oddity happened in about 4.5 percent of all matches. Think of them like teams in baseball underperforming their Pythagorean record calc, or in micro, the 1997 World Series, where the Indians outscored the Marlins, but lost in seven games.
The player with the best record in these "Simpson's Paradox" matches was John Isner (19-5), who played in that unending 2010 Wimbledon match that ended in a 70-68 fifth set. He plays with a forceful serve, and doesn't have a good return game, so he will either blow you out or be blown out in games.
Federer is harder to put a finger on. The researchers theorized that his opponents might take a more aggressive approach to playing him, knowing it's their only chance, and thereby giving themselves a chance for an upset but also giving Federer a chance for many points. But that's more theoretical; the certainty is that Federer never takes any games off:
Second, we can infer that Federer does not engage in any short-term strategic tanking while playing. Unlike some of his peers, Federer doesn't shirk. Even when he loses, the matches are rarely lopsided and almost every individual game is competitive. A nuanced analysis of the chair umpire's point-by-point score sheet in Simpson's Paradox matches would reveal that Federer often wins his service games by a 40-0 or 40-15 count, frequently loses his return games after one or more deuces, and drops tightly-contested tiebreakers when the set score reaches 6-6. In this subset of matches, Federer is just a victim of a scoring system where all individual points are not created equal.