he Swiss, 37, lost to world number 55 John Millman in the quarter-finals, prompting questions about his future.
Federer has scaled down his playing commitments, instead building his schedule around specific events.
“Eventually it catches up with you and you get unexplainable losses and bad performances,” said Cash.
“It will happen once in a while and then a little bit more and a little bit more. Then you say either play a little bit more or retire.
“He may or may not make that decision this time. I’m not saying retirement is imminent but he might think enough is enough.
“When you come towards the end of the career these losses just happen and you scratch your head and ask what went wrong there?” he told BBC Radio 5 live.