Sydney, Jan 13 (Agencies): Frenchman Gilles Simon will play Ernests Gulbis on Friday for a place in the final of the Sydney International, as he recuperating after a knee injury.

Simon, who was hindered by a persistent right knee injury for the first half of last year, wore down Ukraine's Alexandr Dolgopolov 6-4, 6-3 in Thursday's quarter-finals to set up a last-four shot at the third-seeded Latvian Gulbis.

Simon, who reached the quarter-finals of the 2009 Australian Open, continued his fine tournament after ousting Taiwan's eighth seed Lu Yen-Hsun and Portugal's Frederico Gil to line up against Gulbis.

The former world number six said he was now trusting his right knee after suffering chronic inflammation which forced him out of last year's French Open.

"I'm really happy to play without any pain, because a lot of time I had something," Simon said.

"You know one day you don't feel good, you can't do it; the day after it's better, but you're never really confident.”

"It's now two months that I can work on it normally without thinking about it.”

"I'm not thinking any more about where I'm going to put my feet or anything. Just run."

Simon, ranked 41, has missed out on a seeding for next week's Australian Open, making him a dangerous floater in the men's draw.

"If I continue this way, I will come back in the top 20 for Wimbledon (June)," he said.

"Maybe it will be easier because I won't be seeded in the Australian Open.”

"The only thing I know is that I'm playing good. I'm moving very well on the court, as fast as I used to before. So I feel okay."

Gulbis worked his way into the semi-finals after beating Ukraine's Sergiy Stakhovsky 6-4, 6-4.

Gulbis said he pulled up badly from his previous day's win over Russian Igor Andreev.

"Yesterday's match killed me physically," he said.

"It was really humid and I lost a lot of fluids, so I went straight to the hotel and I went to sleep. I didn't feel good.”

"This morning I didn't know if I was going to be able to play, but at the start of the match I felt really good.”

"I will do some treatment. I will go to have a bath, ice massage, whatever it takes. I'm going to be okay tomorrow.”

"I just can't go really long matches (but) don't tell Simon."

Gulbis is the top-ranked seed left in the Sydney draw, after Wednesday's exit of US top seed Sam Querrey and the injury-enforced withdrawal of defending champion and second seed Marcos Baghdatis.

Last year's finalist Richard Gasquet of France was due to meet Serbia's fourth seed Viktor Troicki on Thursday, followed by Germany's Florian Mayer against Italian Potito Starace, to complete the line-up for the semi-finals.