WIMBLEDON, England — Tommy Haas set the tone early with his serve, and he kept his game in tune long enough to upset No. 4 Novak Djokovic and reach the Wimbledon semifinals for the first time.

Now comes the toughest test of all at the All England Club: a matchup against five-time champion Roger Federer.
Haas, at 31 the oldest man in the quarterfinals of this year’s tournament, lost only five points on serve in the first set against Djokovic and finished the 7-5, 7-6 (6), 4-6, 6-3 win Wednesday on Court 1 with 18 aces.
“I served extremely well and didn’t really give him much of a rhythm,” said Haas, a three-time Australian Open semifinalist. “He never really got a groove on returning well to maybe get some confidence or break me.”
But after serving out the first set, Haas stumbled a bit while trying to serve out the second as Djokovic won all four points in the last game to force a tiebreaker. And Djokovic soon held three set points.
“All of a sudden I lost four points in a row on my serve, which before I’ve always constantly held serve pretty easily,” Haas said. “Next thing you know, I’m down in the tiebreak 3-6. Then I just yelled at myself at 3-6, basically, ’Wake up.”’
Whatever Haas did, it certainly revived him, because the German then won the next five points to take the second set.
“That was huge,” said Haas, who also beat Djokovic on his way to winning the grass-court warmup tournament in Halle, Germany, last month.
Djokovic won the 2008 Australian Open and reached the semifinals that year at the French Open and U.S. Open, but he retired in the quarterfinals of this year’s Australian Open and lost in the third round at Roland Garros.
Against Haas, Djokovic played well but couldn’t win enough points when they mattered most.
“I was solid on my service games, but then when I needed to step it up in the important games, I was too nervous in these moments,” Djokovic said. “He took his chances and he played better.
“But I think he was serving really well. And I knew that the key is going to be my return if I’m going to be able to make him play an extra shot. That’s what I didn’t do. So he deserved to win.”
Haas will next face Federer, who is going for his record 15th Grand Slam title. Haas won the first two sets and came within a point of serving for the match against Federer in the fourth round of the French Open on June 1, but he couldn’t hang on.
With Federer serving at 3-4, 30-40 in the third set that day — five points from losing — he ran around his backhand side for an inside-out forehand winner that landed right near a line. That shot spurred a run of nine consecutive games for Federer, who won the last three sets.
“For me that would have been a great success, beating Roger in the fourth round — if it would have happened,” Haas said. “It’s in the past. It’s done. But being a friend of his and knowing how much it meant to him winning the French Open, I’m happy he made that shot.”
After years of struggling with a surgically repaired right shoulder, Haas took the latter part of 2008 off to strengthen it and has played sparingly this season.
Haas is 2-9 against Federer, defeating him at the 2000 Sydney Olympics and in the fourth round at the 2002 Australian Open — both on a type of hard court known as Rebound Ace.
“He’s always been one of the best ball strikers in the game,” said Federer, who considers Haas a friend. “I think he’s really gotten his game together again after some tough injuries.”
Now it’s going to take quite an effort to stop Federer from reaching his seventh straight Wimbledon final.
“I would prefer to play him on Rebound Ace, because I have a lead there, 2-1 against him,” Haas said. “That surface no longer exists. There you go.”