Todd Martin believes that Novak Djokovic has achieved a level of dominance in tennis not seen since Serena Williams was at her peak.
Djokovic had to fight hard to beat Jannik Sinner in the Wimbledon quarterfinals, with the young Italian taking the first two sets.
However, Djokovic reset and refocused himself before managing to turn the match around and move into the semi-finals.
Although he is the top seed at Wimbledon, Djokovic is actually now number three in the world. He is set to slide down to seventh after Wimbledon as a result of the tournament being stripped of it's ranking points.
Despite that, former Australian Open and US Open finalist Martin believes Djokovic's ranking does not really matter.
"I think of Novak [Djokovic] the way I used to think of Serena [Williams] – he is always the favourite, it's always him," Martin told Sasa Ozmo.
"This year has been challenging for him because he hasn't been able to play a lot, but I feel like he's mentally focused and physically in great shape. When that's the case, I still believe he is the best player in the world," said Martin, now the CEO of the International Tennis Hall of Fame.
Although possessing an incredibly powerful armoury of attacking shots, it is the defence that generally wows most about Novak Djokovic.
Part of that is his incredible return of serve, which Martin believes is the best that the game has ever seen.
"That's the key," Martin explained. "Defensive skills were always Novak's strength, and now it's rewarded more on grass, as it is on other surfaces.
"He has the best return of all time, in my opinion. It's going to stay that way until he retires and it's going to be very difficult to find someone who is going to be able to do it better.
"One of the reasons is that his return is equally effective on all surfaces."
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