As Roger Federer keeps winning Grand Slam matches, the history of tennis will continuously be rewritten. Most professionals play for numbers that deal with money; for a champion like Federer, the meaningful numbers can be found in the milestones he attains each time he steps on court.

Federer made more record-keepers and stat geeks happy on Friday afternoon at Wimbledon, prevailing over Tommy Haas in the day’s first gentlemen’s singles semifinal. A close but convincing 7-6 (3), 7-5, 6-3 win over the 24th-seeded German carries Federer into Sunday’s championship match. The triumph possesses the added benefit of burnishing the Swiss superstar’s already gleaming credentials.

For the first two sets of this tussle, the action on the lawns of Centre Court looked a lot like the last match contested by these two men. One month ago in Paris, Federer and Haas dueled in the fourth round of the French Open. On that afternoon, the first two sets were decided by 7-6 and 7-5 scores, just like today’s tilt at SW19. Similarly to this Wimbledon sequel, Federer never faced a break point in France during the first set, while Haas–serving huge in his own right–steered the set to a tiebreak. In the second set on the red clay of Roland Garros, Haas made a late push at 5-all, breaking Federer for a two-set lead. Yes, the Swiss rallied over the final three sets to take that match in five, but for most of that day at Court Philippe Chatrier, Federer had little room for error against his friendly 31-year-old foe. The match was, without question, the toughest on Fed’s road to his elusive French Open title.

Friday at the All-England Club, Federer didn’t need five sets (or even four) to dismiss Haas, but the quality of the combat remained spirited and relatively even. The difference between Paris and suburban London–besides the playing surface, of course–was the fact that Federer managed to win the first-set tiebreak, thanks to a bold backhand return that gave the No. 2 seed a 5-3 mini-break advantage he would not relinquish. That display of composure on the part of Federer was enough to change the course of the competition. The 7-3 tiebreak win allowed the 14-time Grand Slam champion to breathe a little more freely. Had Haas been able to steal the first set, a replay of a June joust on red clay could have easily unfolded in early July on grass.

As it was, Haas still made a bold charge at the heavy favorite, pushing the second set to 5-all with continued clutch serving and a deceptively powerful backhand that gave the Swiss problems in extended rallies. Federer leaned on his serve for much of the match, but Haas often enjoyed a great amount of comfort from the baseline. Just one more service hold from a tiebreak, Haas had to feel optimistic about his prospects when he toed the line at 5-6 in the second set.

But that’s when the five-time Wimbledon champion decided to put his foot down.

Just as Haas secured a late break to win a 7-5 second set at the French, Fed turned the tables to snag a 7-5 second stanza in this particular passion play. While the German underdog struggled with his first serve and felt the weight of the moment, Federer ripped a crowd-pleasing crosscourt forehand to earn a break point that doubled as a set point. Just moments later, an extended rally–the kind of exchange Haas had been winning for most of the set–ended with the 24th seed overcooking a forehand. In the blink of an eye, a set that had “tiebreak” written all over it had become a portal to an easier afternoon for Federer.

Haas would stay in the thick of the fight through the first seven games of the third set, but at 3-4, the German fended off four break points, only to lose a fifth with a tired backhand into the net. Federer, who never faced a break point all afternoon and was rarely pushed to deuce in his own service games, cleanly served out the match at 5-3, sparing himself of the need for five sets of work. Haas acquitted himself well in a match that didn’t differ all that much from last month’s fistfight in France; Federer, however, won the handful of key points in the opening sets… the very same handful of points that didn’t go his way in Paris. That’s why statisticians and tennis historians have so much to write about before Sunday’s final.

Just what numbers are being bandied about as Federer marches onward at Wimbledon?

* 20. That’s the number of Grand Slam finals Fed has now reached, the most for any male tennis player. The Swiss entered the day tied with Ivan Lendl (19 slam finals), but now, the No. 2 seed is number one on the all-time list.

*16, 17. Federer’s win means that the Swiss has now reached 16 finals in the past 17 slam tournaments, a phenomenal stretch of excellence made possible by his greatest streak, the run of 21 consecutive appearances in slam semifinals. Speaking of slam semis…

* 18-3. This win over Haas gives Federer an 18-3 record in that span of 21 straight Grand Slam semifinals. The other two semifinal wins in Fed’s slam career came before the beginning of that 21-tournament streak.

* 7. Pete Sampras might have won seven Wimbledons, the most in history, but he didn’t win them by reaching the finals on an uninterrupted basis. Federer has “only” five titles at this prestigious tournament, but this triumph today allows the world No. 2 to appear in a seventh straight Wimbledon final, a distinction unmatched by any other man in history. William Renshaw (1882-’87), Wilfred Baddeley (1891-’96), and Bjorn Borg (1976-’81) all reached six straight Wimby finals (in the era shared by Renshaw and Baddeley, the defending champion gained an automatic berth into the final), but Fed now stands alone at seven.

* 6. Federer has an active streak of six straight Grand Slam finals.

* 1. No, that’s not Federer’s current world ranking (though it will be when Wimbledon ends), but it points to the number of people other than Rafael Nadal who have beaten Federer at a Grand Slam event since the 2005 French Open. That’s right–only one man other than Rafa has beaten Fed in the past 18 majors: Novak Djokovic in the 2008 Australian Open.

That’s enough numbers for now. If Federer wins on Sunday, we all know what number will dominate the headlines then: 15.

Not much needs to be said on that count.