Roger Federer’s been at this tennis racket for a while now, long enough to know when it’s time for a change.

Following a year that saw him fail to make a grand slam final for the first time since 2002, and suffer a humiliating Wimbledon defeat against Sergiy Stakhovsky, many were worried Federer had fired his last shot.

But he’s emerged in 2014 with a body that’s allowing him to do things he struggled to for much of last year, and a racquet that, if you listen to the experts, is allowing him to do things he’s never done before.

Change, that toughest of concepts for an athlete to embrace, doesn’t come easy at any age.

At 31 and with more wins to his name than the Harlem Globetrotters, Federer could have been excused for taking a nice, easy road into retirement.

But Federer is no ordinary athlete.

His Australian Open fourth-round win over Jo-Wilfried Tsonga on Monday night was like jumping in the DeLorean and taking a little spin back to 2007.

The debate now is whether Roger’s improvement is down to him shrugging off a nagging back problem, or whether his new Wilson racquet is enabling him to do what Cher could never quite pull off – turn back time.

According to a New York Times report, Federer first asked Wilson to build him a new larger prototype racquet more than a year ago and he spent time throughout 2013 testing various designs, before going back to his original for last year’s US Open.

Most top tennis players use a racquet with a head size of between 98 and 100 square inches, while during Federer’s glory years he used a head of 90 square inches.

He arrived Down Under with a new all-black 98-square-inch prototype, considerably larger than the one that had carried him to grand slam glory 17 times throughout the past 10 years.

The best-known Wilson since Cast Away? Photo: Getty

He looked reborn on Monday night and, after Federer had crushed a high backhand return winner cross court (above), commentator Jim Courier thought he had seen firsthand evidence the racquet was having an influence.

“I don’t think I’ve ever seen him be able to hit that shot before,” Courier said on Channel 7.

“For me, that’s the racquet coming into play. That’s why you want that racquet, because that is what you have to hit against Rafa all the time – the high backhand.”

The theory goes that the bigger the head, the bigger the ‘sweet spot’ and the larger the margin for error.

When asked whether his new racquet had helped him with certain shots Federer replied: “Yeah, I think so. I did return really well tonight.”

“I had good timing. I was also reading the serve well, not like other times.

“It was smooth for me. I do believe I have easier power with the racquet on the serve. It might help me on the return, as well. I hope it is the case.

“I still need to put many more matches and hours on it, but so far so good.  It’s a great start to the season with the racquet, with my body.”

Beating Tsonga is one thing, and it’s an achievement not to be sneezed at given the Frenchman’s standing, but the real test, for both Federer and the Wilson, is yet to come.

Andy Murray awaits, and when that match comes we’ll see if there’s any plutonium left in Federer’s flux capacitor.