(CNN) -- Roger Federer had to work a little harder than he did Friday but the 17-time grand slam champion rallied past Tommy Haas at a Wimbledon warm-up in Germany to move one match away from winning his first title of the season.
In a battle of players over 30 -- Federer turns 32 in August and Haas is 35 -- the Swiss came through 3-6 6-3 6-4 in Halle. Mikhail Youzhny awaits in the final.
In the quarterfinals, Federer dispatched Haas' fellow German, Mischa Zverev, 6-0 6-0 in under 40 minutes to register only the second 'double bagel' of his glittering career.
Zverev was a wildcard ranked 156th and so Federer knew he would be tested more in the last four against Haas, who beat him in the 2012 Halle finale.
"Clearly I wasn't sure how well I was really playing coming into the semis," Federer said. "Happily I was able to maintain a really high level of play.
"After losing the first set there is not much margin for error anymore."
Federer has endured a difficult campaign -- by his standards. His only other final came at May's Rome Masters on clay, where he was beaten by Rafael Nadal in straight sets.
Then at the French Open he was upset by Frenchman Jo-Wilfried Tsonga in the quarterfinals.
His last grand slam final came a year ago at Wimbledon when he downed home favorite Andy Murray for a seventh title at the All England Club.
"Honestly I'm playing pretty good for a long period of time," he said. "Clearly I'm very happy to play the final tomorrow. It is a big final for me. After this we'll focus on Wimbledon."
If Federer defeats Russia's Youzhny on Sunday -- Youzhny, too, is a veteran who turns 31 this month -- he would capture his sixth title in Halle but first since 2008.
Their head-to-head record suggests Federer should be the heavy favorite. He leads Youzhny, a 6-3 6-2 winner over second-seed Richard Gasquet on Saturday, 14-0.
Murray in London final
Center Court in Halle benefits from a roof but it's not the case at the Queen's Club in London, and the other men's Wimbledon warm-up this week has been affected by adverse weather.
More rain Saturday led to both semifinals being delayed, with organizers eventually shifting one to an outer court.
Eventually Murray, like Federer, came from a set down to progress to the final. He beat fourth-seed Tsonga 4-6 6-3 6-2 in his first event since returning from a back injury, saving two break points at 3-3 in the second set.
"I managed to turn that match around against a top player," Murray told the BBC. "He's one of the best grass-court players in the world."
At almost the same time, defending champion Marin Cilic ousted four-time tournament winner Lleyton Hewitt 6-4 4-6 6-2.
With rain expected Sunday, organizers moved the final to 12 p.m. local time, two hours earlier than originally scheduled.