Working for BBC's Radio 5 Live, Cash called the lengthy break "legal cheating" and hit out at the 18-time grand slam champion.

"It's cheating and it's being allowed. It's legal cheating but it's still not right," Cash said.

Federer took a time out during his semi-final win over Stan Wawrinka after his countryman also took medical break.

"My leg has been hurting me since the (second round) Rubin match," he said.

"I was able to navigate through the pain. For some reason against Stan I had it from the start on both sides of the groin.

"I felt my quad midway through the second set already, and the groin started to hurt midway through the third set.

"I just told myself, The rules are there that you can use them. We shouldn't be using these rules or abusing the system. I think I've led the way for 20 years.

"So I think to be critical there is exaggerating. I'm the last guy to call a medical timeout. I don't know what he's talking about."

When quizzed on Federer's time-out, Nadal said he had "no opinion" on the matter. 

Federer’s win makes him an 18-time grand slam champion.