Kohlschreiber is into Halle's semi-finals for the fourth time in his career after securing a 7-6 (7-4), 6-3 win over the former world number one in exactly 90 minutes.
"It could have gone either way. It was very tight in the first set, I didn't have a lot of luck in the tie break," admitted Hewitt with Wimbledon set to start on June 20.
"He played extremely well and served well throughout the entire match. It's been perfect preparation for me here after a few months out.
"I didn't come here with any expectations and it's been nice to get some matches here and feel comfortable on the grass."
Kohlschreiber smashed down 14 aces, compared to the Australian's nine, in a hard-fought match and the defeat means Hewitt, who is making his comeback after ankle surgery, is now set to drop out of the top 100 in the ATP rankings.
"Today, I could see an improvement in my game - everything was just fine and I often had a bit of luck on my side," said Kohlschreiber.
"I couldn't do much wrong. This match was good - although he is coming back from injury, Lleyton Hewitt is still one of the best players in the world.
"Now the bar has been set high. The next game will be hard, no matter who is on the other side of the net. Form on the day will decide the match."
It was Kohlschreiber's strong serve which carried him to victory and he will play Gael Monfils, ranked ninth in the world, in Saturday's semi-final after the Frenchman beat Germany's Florian Mayer 6-4, 6-4 in little over an hour.
"I am happy," beamed Monfils, who has won over the crowds here.
"I came here with the expectation to play like a top-10 player and I did that.
"It is always tough for me to adjust to grass. Last year I played three rounds in Wimbledon and this year I wanted to have a good comeback on grass.
"My movement on the court is great and I know, it will be a good match against Philipp (Kohlschreiber).
"I am happy that I have had such a good preparation for Wimbledon here in Halle."
After the withdrawal of world number three Roger Federer on Monday, Tomas Berdych became the top seed and the winner of the 2007 tournament had few problems as he enjoyed a 7-6 (7-3), 6-1 win over fifth seed Viktor Troicki.
The firm surface at Halle is favouring the strong hitters and this was a battle of the big guns as Berdych smashed down 13 aces, compared to the Serbian's 11, as both players contributed to 14 aces in the first set alone.
Berdych will meet Philipp Petzschner in his semi-final after the German booked his place by knocking out eighth-seeded Canadian newcomer Milos Raonic.
In a tough last-eight match, Petzschner needed nearly two hours to prevail over 20-year-old Raonic and seal a 6-3, 6-7 (6-8), 6-3 win.
"It was a tight match on a knife edge. I nearly won it in the second set," said Petzschner, who also reached the semi-finals here last year.
-AFPTags: sport, tennis, australia, germany First posted June 11, 2011 08:02:00