Greg Rusedski believes Roger Federer will go into Wednesday's Australian Open quarter-final against Andy Murray in his best form since winning his seventh Wimbledon title.
In the summer of 2012, Federer beat Murray under the Centre Court roof to collect his 17th grand slam trophy.
Since then the Swiss has managed just one slam semi-final - losing to Murray in five sets in Melbourne 12 months ago - and saw his run of 36 consecutive quarter-finals ended at Wimbledon last summer.
But in a comprehensive defeat of Jo-Wilfried Tsonga on Monday, Federer looked back to his best, while Murray dropped his first set of the tournament against lucky loser Stephane Robert.
The Frenchman was the third of Murray's four opponents so far to be ranked outside the top 100, allowing the Scot a gentle reintroduction to grand slam tennis following back surgery.
Former British number one Rusedski, who is working as a pundit for Eurosport, said: "It was good for him to be tested and overall I think it was an excellent performance from Murray.
"I think he's improved with every match he's played throughout these championships. I thought the first two sets were absolutely brilliant, he dictated play and that's what you like to see from Murray.
"If anybody was worried about his movement, there was nothing to worry about.
"I think Murray enjoys playing Roger Federer but Federer's tactics have been a lot better this year. I think Roger will want to attack Andy's second serve, which Robert did, which changed that third set around in his favour.
"Federer was extremely impressive - that's the best I've seen Federer play since his Wimbledon title. He was sensational - the movement, the balance, when to come in and when to do the right things.
"Everything he did was just right."
Murray leads his overall head-to-head with Federer 11-9 but last year's semi-final is the only one of their four grand slam meetings that the 26-year-old has won.
"It's a big match for me," he said. "I said at the start of the tournament, I can't honestly say my expectations are as high as if I'd been playing for the last four months.
"It's been a good effort so far to get to the quarter-finals of a slam this soon after back surgery.
"So I'm happy with that. But I'm not far away from winning the event. Anyone that's in the quarters is close. I just look forward to that match and hopefully I'll play a good one."
Federer had his own struggles with back problems last season and appears to be living up to his promise that his form would pick up once he felt fully healthy.
The Swiss said: "I don't have doubts any more. I know I'm going definitely in the right direction.
"Last time we played it was a great match. So I hope we both can reproduce something similar."