Andy Roddick reflected on the key transformation Novak Djokovic made that ultimately helped him become a winning machine.

Roddick faced Djokovic over a five-year period from 2007 to 2012 and would go on to hold a 5-4 head-to-head record against the Serbian superstar. The American notably won five of their first seven meetings and it was during that time where Djokovic was injury prone and pulled out of matches.

It was even such that Roddick would intentionally extend rallies with Djokovic as his physicality and conditioning was seen as his weakness.

Of course, that is now history as Djokovic is regarded by most as the fittest tennis player today which all comes from taking care of his body — and he's still going strong at the age of 36.

“Novak’s progression, just on the physical side, has been unlike anything I’ve seen in pro sports,” Roddick wrote in a blog for Betway. “When I used to match up against Djokovic – and I had a solid record against him – I wanted to keep him out there, I wanted to extend rallies. Now, that’s a surefire way to lose.

“The way that he’s taken care of his body, not just from a training standpoint, but from a dietary standpoint, has left no stone unturned. He’s been such a professional throughout the years. He took a weakness and turned it into one of the biggest strengths that we’ve seen in professional tennis. I give him so much credit for that.

“It will be weird for the tennis universe when Novak moves on. We’ve become almost entitled to watching the greatness of these players for so long now.”

Djokovic did, however, lose the Wimbledon final last month to Carlos Alcaraz in a result many believe signals the changing of the guard.

Roddick, in particular, was shocked by the result, especially given that Alcaraz was able to defeat the 23-time Grand Slam winner on grass.

“I was shocked by the result of the men’s Wimbledon final,” Roddick said. “Two months ago, I don’t think anyone would have predicted Novak being beaten on grass. His dominance on the surface over the last 10 years has actually been underreported, in my opinion. Grass is one of those surfaces that, as a young player, it normally takes a couple of seasons to grasp, but Alcaraz is a different type of dude.

“He struggled in the first round of Queen's, didn't look completely natural on the surface, but by the end of the tournament he looked like he'd been playing on it for 10 years. That fifth set was the first time in a long time that I've seen Djokovic on his heels. The way that Alcaraz is able to create speed, open up his shoulders and push his opponent around is so impressive.”

In the end, Roddick believes that result is further proof that the Spaniard is the real deal.

“We’re coming to the tail end of the Big Three era, and we thought we might not see anything like that again, but Alcaraz has come in and thrown that logic out the window,” he added. “I didn't expect to have a new force who plays as dominantly as those great champions present himself this quickly.

“This kid is the real deal. Not only do I think he’ll win double digit Slams, but I've had as much fun watching him as I have anyone since I started playing.”