Roger Federer put a poor start behind him to beat Carlos Moya 4-6 6-4 6-2 and reach the final of the Hamburg Masters.
Federer, needing every bit of match practice he can get on clay before the French Open, seemed determined to go for his shots from the start and he initially paid the price for this high-risk strategy.
The world number one hit 20 unforced errors in losing the first set to the unseeded Moya before finding his rhythm and winning in two hours seven minutes, finishing off with a stinging forehand pass.
Victory for Federer means he will face second-seeded Spaniard Rafael Nadal or Australian 16th seed Lleyton Hewitt in the final.
Nadal, the second seed in Hamburg but the overwhelming favourite, has won 80 consecutive matches on clay going into his semi-final, dating back to April 2005.
Federer showed signs that he may be emerging from his slump with a patchy but fighting display against the former world number one, which carried him to only his second final appearance in two-and-a-half months.
The Swiss admitted that the stress of having to make the decision to part company with coach Tony Roche had been influencing his form.
'I take decisions like these very seriously and I thought a lot whether this is the right decision because he is one of the best coaches on the tour and you don't want to get rid of him just like that.
'I was disappointed I couldn't block that out (in a shock loss to Filippo Volandri at the Rome Masters). But my confidence is okay now.
'I was not confident in my match against Volandri, but there were reasons and now I am feeling good.
'I was disappointed I couldn't serve out the second set at 5-3 (against Moya), but my confidence is okay now. My game is getting a better feeling. I feel my problems are solved.'
Federer emerged from error-prone phases against Moya with great shots when he needed them, especially at 30-40 in the third game of the second set, when a great backhand counter-hit got him out of trouble and helped him back to deuce.
Then again in the third game of the final set Federer found himself at 15-40 down, and came up first with a heavy topspin forehand - the shot least likely to let him down - and then a potent net attack.
Federer often gambled to get to the net, and sometimes appeared to pursue risky strategies, perhaps with half an eye to preparation and practice for the French Open in eight days time.
These were cool and heavy conditions in which the slightest mistiming of the ball could lead to a mistake, and Federer's unforced error statistics were high, as they had been all week.
But Moya played with great intelligence, considerable resilience and a threatening forehand, and, after disposing of three seeds, Blake, Berdych and Djokovic, clearly thought he could win.
'I was a bit disappointed with the result because I though this was a day when I could have beaten Roger,' Moya said.
'I felt there was a good chance but it didn't happen. He played his best at the right moments and I didn't.
'I played very deep with my backhand and so I was pleased with the way I played. Maybe things could have been different if I had broken in the third game of the second set. But when I look back next week I will realized that I have had a great tournament.'
The last four games however saw Federer accelerate and produce the kind of form he will need if he is to have a chance of relieving Rafael Nadal of his French Open title.
He hit two hurtling aces in the penultimate game and finished the match with a wonderful forehand pass taken deceptively from the backhand side.
Federer then held his arms aloft and threw them down again violently, as though the victory had been a relief rather than a triumph.
