Roger Federer says he has seen "improvement and no setbacks" since returning to the tour in March after over a year out due to two knee operations.
Federer, who turns 40 later this year, has taken time off from tennis since winning three matches at the French Open against Denis Istomin, Marin Cilic and Dominik Koepfer before withdrawing from the clay-court Grand Slam to protect his body after a gruelling third-round win over the German.
The Swiss superstar played his first match back in Doha but said he was targeting full fitness for the grass-court season and wants to reach his peak by Wimbledon, where he has won eight of his 20 Grand Slam titles.
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"I probably would have taken the place I am in today," Federer said in Halle, where he will be competing for an 18th time and holds 10 titles.
"March was still very early days for my comeback but I just felt like it was a good time to come back. I thought that Doha actually went extremely well overall because I know my expectations were close to zero over there. So I'm happy I was able to play two competitive matches over there.
"Ever since I've only seen improvement, no setbacks. After I guess the two operations I have to be extremely careful with every move I do. But now it's really go time. This is essentially where the season really hopefully starts for me."
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Federer has been undertaking low-intensity practice for 30 minutes over the last few days and feels his body has recovered from the rigours of Paris.
"The knee just needs always extra care, and I hope it's also going to react well to the grass," he said, adding that he feels "all my strengths get amplified" when he plays on grass.
"I'm going to probably push a little bit more in practice this afternoon or maybe tomorrow, just to get the body ready for the grass courts, and I hope I have no negative reactions.
"I'm pretty positive about my chances. I'm confident that somehow I'll be fine in the coming days. But of course I want to stay injury-free. That's the most important (thing) right now."
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