Former WTA star Andrea Petkovic believes Roger Federer would have retired sooner if not for the rest of the Big Three.

Federer only retired from action last year as he called time on a legendary career that saw him dominate tennis for a good period and eventually finish with 20 Grand Slam titles.

He has since been eclipsed by Novak Djokovic (23) and Rafael Nadal (22) and if not for the duo, he may have retired a lot sooner. In fact, Petkovic believes the Swiss legend would have stopped right when he got 17 Grand Slam titles.

“If we go back to 2009, when Roger Federer broke Sampras' number. If Rafa Nadal & Novak Djokovic hadn't appeared, Roger would've stopped at 17 Slams,”Petkovic was quoted as saying by TennisUpToDate.com. “100 percent. We would've never seen these numbers.”

It's certainly a bold yet interesting claim.

In 2009, Federer broke the previous record (14) held by Pete Sampras by winning his 15th Grand Slam trophy following a grueling 5-7, 7-6, 7-6, 3-6, 16-14 victory over Andy Roddick in the Wimbledon final.

Federer would go on to win the Australian Open in 2010 and Wimbledon in 2012 to take his record to 17, but wouldn't win another Grand Slam title for another five years.

In that time, Nadal and Djokovic were slowly catching up to Federer as they reached 14 and 12 respectively going into the 2017 tennis season.

Federer would eventually end his drought by winning the Australian Open in 2017 followed by victories at Wimbledon that year and the Australian Open the following year to take his tally to 20.

One would imagine that would have been enough to retire on but that clearly didn't turn out to be the case with Djokovic potentially becoming a 24-time Grand Slam winner if he emerges victorious at the US Open later this month.