Roger Federer added another highlight to his age-defying career resurgence Friday, returning to the top of the world rankings for the first time in more than five years and becoming the oldest player to reach the top spot.
'It was extremely complicated tonight, ' he said after the win.
Federer recovered, however, to get the tiebreaker level and then create four set points of his own, finally converting the last one by hitting a forehand victor.
Yet Federer, for all the unique magic that other players can only dream about, offers a far more pragmatic explanation for his ability to make a mockery of the ageing process. Kohlschreiber, 34, had not beaten Federer in 12 attempts but on his own service game proved a tough opponent for the Swiss, pushing him all the way to a first set tiebreak. I think Philipp did that to me; it was a struggle.
"Today when the score was close I couldn't release my shots so it was quite a battle".
But Federer has since overseen a scarcely believable new era of dominance, and his triumph at last month's Australian Open was his third victory at the last five grand slams, and his 20th major in total.
GETTYRoger Federer has won three of the last four Grand Slams he has entered
"I was preparing for the second set, being down one set. What I did past year and what Rafael (Nadal) is doing also is maybe a bit of a lighter schedule", he said this week in the Dutch port city. "I just don't see it happening where he's not successful".
Both men squandered set points in the first but it was Federer who converted when it mattered most to get his nose in front. "I'm very excited for tomorrow's match, I can't wait for it to come around", he had said coming into the match against Haase.
"Sometimes at the beginning you get there just because you play so well".
Russian Daniil Medvedev joined his compatriot in the last eight by beating Pierre-Hugues Herbert of France 3-6, 7-6 (7/2), 6-4.
Meanwhile, in the bottom half of the draw, last year's runner-up David Goffin progressed to the last four without having to hit a ball after the withdrawal through illness of Tomas Berdych.