Even Roger Federer had doubts. As he slid in the rankings and losses came more often, the Swiss great admitted that he too wondered if he had it in him to challenge for another grand slam.
Now he has no doubts.
Privately he already knew that before this week. Publicly it became abundantly clear on Monday night with an effortless sweep past Jo-Wilfried Tsonga in three sets, 6-3, 7-5, 6-4, to the quarter-finals of the Australian Open for the 11th successive time.
He did so in such an elegantly complete manner that his game looked even better at times than when he had been at his best.
"For me personally, I've overcome it. I don't have doubts anymore. I know I'm going definitely in the right direction. I've had a great off-season. I had a strong end to the year. I couldn't have worked harder in the off-season," Federer said of his present mindset in grand slams.
Asked if beating Murray in the quarter-finals would validate that feeling, Federer said he needed no further proof.
"(Beating Tsonga) is a big test for me. I don't need Murray to have a further test. The draw is a very testing draw … What I've shown over the last three to four months to myself is that I'm more confident, that I know I'm most likely going to play okay in my next match, which wasn't always the case midway through last year when I didn't know how I was going to feel actually during the match.
"Now I feel like I can think ahead. I can think tactics. I can think many things out there. Everything else but my body, and that's very positive. I've overcome a lot in the last few months."
Federer broke Tsonga in his first service game and, looking as sharp as a new haircut, held his advantage for the set. His game looked as breezy as it has for some time with his driving one-handed backhand, serve and court movement returning to that level that reaches 11 on the dial.
Tsonga, the 10th seed, is a man not lightly disposed of – last year the pair played one another here and Federer took five sets and more than three-and-a-half hours to claim the win.
A measure of how emphatic this victory was is evidenced by the fact Tsonga managed only one break point on Federer’s serve in three sets. He lost it.
The second set was as thoughtful and confident as the first. Federer was aggressive and approaching the net in a way that was more than vintage; it appeared to be more than he had even in his salad years. It was a plan, encouraged by his new coach Stefan Edberg.
"I used serve-volley against (Pete) Sampras in 2001 at Wimbledon. It's not like I've been standing way back in the court like some clay courter. I've always tried to come in," he said.
"I was actually coming in a lot at the beginning of my career because I didn't feel I was good enough off the baseline against the great baseliners that were still in the game in my time: Hewitt, Ferrero, Safin, Nalbandian, Agassi.
"Eventually in 2003 I probably realised I can actually also hang with them from the baseline and beat them. That's when everything changed. Conditions got slower. I improved from the baseline. My movement got solid. I was fit. That's when I went on a run. But I've always enjoyed coming to the net."
Tsonga said Federer had played "unbelievable" tennis.
"I was not surprised because, you know, when you play Roger, you expect him at this level," Tsonga said.
"You know he's able to play like this, so you always expect it."
He said he just couldn't find a way to stop Federer's momentum. "I was not enough good, you know, to give him a good opposition, and that's it."