Rafael Nadal has "positive feelings" about his health having previously said his knees would determine how effective he can be at Wimbledon.
The Spaniard made history by clinching his 10th French Open title last month but admitted in the aftermath the troublesome joints would play a large role in his chances of a second successive major win.
Nadal has long struggled with tendonitis in both knees, a problem that reached its peak in 2012.
In his first outing on grass this season, the world number two emphatically saw off John Millman 6-1 6-3 6-2 on No.1 Court. However, he was unwilling to get ahead of himself.
Nadal said: "My knees are ready for the second round probably, that's all.
"And I am happy that I am here playing again in Wimbledon and with positive feelings in terms of health. That's the most important thing.
"I always expect to go on court and compete well, try my best. Things sometimes goes better, and things sometimes goes worse.
"It was a very positive match for me, a good start. That's doesn't mean a lot. The only thing that means was today was a very positive start. I am through to the second round. That's a very important thing for me.
"And I'm happy because I didn't win a lot of matches [over the] last couple of years here in Wimbledon. Today I win one, and I am looking forward to play the second one."
Donald Young will be Nadal's opponent in the second round.