Roger Federer's old coach Ivan Ljubicic has made his feelings on Novak Djokovic crystal clear.
The Serb may have lost to Carlos Alcaraz in Sunday's Wimbledon final but still has 23 Grand Slam titles to his name.
That's one more than Rafael Nadal and three greater than Federer, who announced his retirement last year.
Now, Ljubicic has opened up on both Federer and Djokovic - insisting the Serb's achievements don't tarnish what his old student managed to do during his time in the sport.
Roger Federer's old coach has opened up on Novak Djokovic rivalry
PA
"You may not be objective in this," he told Tages Anzeiger.
"For me, the best is the one that has had the greatest impact on your sport.
"Novak is the most successful. He has all the statistics, but there is a difference between being the largest and the most successful.
"Michael Jordan was not the most successful, but everyone considers him the greatest for his influence on the sport.
"Not all of us have to agree. What Novak has done does not tarnish what Roger did."
Federer recently attended Wimbledon to watch Andy Murray in action and was honoured at Centre Court.
It's unclear what the future holds for the 41-year-old, who is currently enjoying some time with his family in Spain.
Some have wondered whether Federer could venture into coaching one day.
But Ljubicic can't see that happening and said: "I can't imagine him being a coach. I see him more as a mentor.
"He loves helping, but I don't see him wanting to make the commitment that being a coach requires.
"He likes to do many things."
Ljubicic has said similar in the past when it comes to the GOAT debate, confessing last month: "I feel that Novak is the most successful already, but the word ‘greatest’ implies subjectivity and personal preference.
"I think that’s good, to be honest – everybody has a preferred GOAT and let the discussion begin.
"If we look at other sports, for example is there a (definitive) GOAT in football.
"In basketball everybody agrees that it’s Michael Jordan, but he’s not the one with the most trophies.
LATEST DEVELOPMENTS:
Novak Djokovic has won three more Grand Slam titles than Roger Federer
PA
"It’s someone that influenced you personally mostly: for a third of the world it’s Federer, for the other third of the world it’s Nadal and for the final third it’s Novak.
"If Novak wins a few more Slams – which seems likely at this point – then the debate becomes meaningless.
"If Novak ends up having five to ten more than the others, we won’t have conversations like this anymore."
After losing to Alcaraz, Djokovic will now be hoping to add to his glittering Grand Slam collection when the US Open kicks off in August.
The former world No 1 was banned from competing at the competition in 2022 due to his unvaccinated status, but is expected to feature at Flushing Meadows this year.
