Roger Federer said on Saturday that the back pain that has hindered him recently is under control, and his focus is on defending his title at the Cincinnati Masters.
The Swiss, who celebrated his 32nd birthday on the practice court in the muggy Midwest venue on Thursday, is counting on "passion" to re-ignite his tennis after Wimbledon disappointment followed by injury-plagued weeks on the clay courts in Hamburg and Gstaad.
"My passion is sky high. If the passion doesn't overweigh all the rest, the end is extremely near," said Federer, who won his fifth Cincinnati title in 2012. "You might be doing it for the wrong reasons. But I love what I'm doing."
The fifth seed starts with a bye in the tournament that begins on Monday.
He pronounced himself "fit and mentally motivated" going into an event in which the men's field is headed by Novak Djokovic and Andy Murray, and keen to "get back into playing well and getting deep into tournaments."
Federer said he made late entries last month into the pair of European clay events in the hope of forgetting his Wimbledon second-round loss to Sergiy Stakhovsky, and also to try out a new, larger racquet head after 15 years with a smaller model.
The racquet project quickly became an afterthought as back pain kicked in during the Hamburg tournament and contributed to a first-match defeat in the Swiss alpine village of Gstaad.
"I wanted to get over Wimbledon as quickly as possible. I was ready to go in Hamburg and tried to enjoy playing. But I had too many problems in the back and the body, they came up gradually.
"In Gstaad I was not prepared. I played OK, it was not like I couldn't play at all."
But the 17-time Grand Slam winner confessed: "It was frustrating not to be able to play proper tennis.
"I really didn't want to pull out of Montreal (this week) but it gives me more time to prepare here," added Federer, who arrived Stateside on Wednesday.
Federer said he plans to keep using his new racquet and has liked what he has seen in the limited time he has had with it.
"But I couldn't focus on the racquet, so I really don't know how I was feeling the balls. Right now I'm happy with the prototype and plan to keep playing with it here," he said.