Rafael Nadal called for tougher sanctions against players who abuse tennis officials on Thursday in the wake of the controversial suspended sentence handed down to Alexander Zverev.
Spanish star Nadal said that as a friend and practice partner of Zverev, he had no desire to see the German Olympic champion receive a stiffer sentence for his violent outburst at last month's Mexico Open in Acapulco.
But the 21-time Grand Slam champion said that as a fan of the sport, tougher sanctions were needed.
Zverev was disqualified from the tournament for repeatedly smashing his racket into the umpire's chair before verbally abusing the official.
On Monday the 24-year-old was given a suspended eight-week ban and $25 000 fine for the incident – penalties decried as too lenient by some.
Speaking ahead of the ATP/WTA Indian Wells Masters tournament in California on Thursday, Nadal said more stringent punishments should be levied in future.
"It's so difficult to talk in my position because from from one point of view, I have a good relationship with Sascha (Zverev)– I like him and I practice with him very often," Nadal said.
"I wish him all the very best and he knows that he was wrong, honestly, and he recognised that very early.
"So that's a positive thing in his side, in my opinion.
"On the other hand ... if we're not able to control and create a rule or a way to penalise this type of attitudes a little bit in a stronger way, then we as a players, we feel stronger and stronger all the time.
"We need to be a positive example, especially for the kids watching us.
"So from one side, I don't want a penalisation for Sascha because I like him and I have very good relationship with him.
"In the other hand ... I'd like to see something harder for this kind of attitudes, not only him, I mean in general terms because this protects the sport and protects the referees."