Spain’s Rafael Nadal returns to Germany’s Rainer Schuettler during a semifinal match on Centre Court at Wimbledon, Friday. Nadal will meet Roger Federer tomorrow in the finals. (AP Photo/Alastair Grant)

WIMBLEDON, England — Add up all of Roger Federer’s greatness on grass courts, and the numbers are striking: 40 wins in a row at Wimbledon, 65 overall on the surface. Now he seeks an additional victory, a victory that would make him the first man since the 1880s to win six consecutive Wimbledon titles, a victory that would give him a 13th Grand Slam championship, one shy of Pete Sampras’ career record. And a victory that would have to come against his only real rival in today’s game, Rafael Nadal. No. 1 Federer and No. 2 Nadal set up their third straight showdown in the Wimbledon final, and sixth meeting in a major title match, by handily beating unseeded opponents Friday. Federer eliminated Marat Safin 6-3, 7-6 (3), 6-4 in the first semifinal, and Nadal defeated Rainer Schuettler 6-1, 7-6 (3), 6-4. ‘‘There’s one more left,’’ Federer said. ‘‘I don’t think it matters really a lot if I’m the favorite or not. I’m on an incredible winning streak on grass.