MELBOURNE, Australia

Roger Federer shanked a few shots and was unsettled by how nervous he felt after six months on the sidelines, despite the familiar surroundings at the Australian Open.

No other man on tour knows the way around a Grand Slam tournament better than Federer, who is playing in his 69th major and has won a record 17.

He served 19 aces and had only one double-fault in a 7-5, 3- 6, 6-2, 6-2 win Monday over fellow 35-year-old Jurgen Melzer, but dropped serve three times and experienced frustrating moments.

“I was feeling nervous once the match actually started,” said Federer, who hadn’t played at tour level since Wimbledon after taking time off to let his injured left knee heal. “In the warm-up … I felt fine. Then I hit four frames in a row. It was like, ‘Whew, it’s not as easy as I thought it was going to be.’

“I struggled for a while to find that groove, that rhythm.”

Federer had surgery on the knee after a semifinal exit at the last Australian Open and missed the French Open, ending his streak of 65 consecutive Grand Slam tournaments. He returned for Wimbledon, reached the semifinals, then didn’t play again in 2016. In November, he fell out of the top 10 for the first time in 734 weeks.