Former American number one James Blake finds it hard to envisage Roger Federer catching Jimmy Conors' record of 109 singles titles.
Federer has had a career renaissance in 2017, winning the Australian Open, Wimbledon as well as an overall total of seven titles in the calendar year at a remarkable 36 years of age.
His most recent win was the Basel Open where he defeated Juan Martin del Potro in the final to win the Swiss Indoors title for the eight time as well as his 95th ATP singles title.
Federer, regarded as the greatest tennis player of all time, could further cement his legacy by winning 15 more titles and overtaking Connors' record.
However, Blake believes catching the American will prove too hard for the Swiss ace, especially considering his age.
"109 is just too much. I still love Roger, he is the greatest of all time in my opinion, but 109 is just too many at this point in his career," Blake said, as quoted on the Express.
"He's going to really pair down his schedule, only playing the biggest events, Grand Slams, Masters 1000s, Basel, a couple others.
"It's just so tough to expect him to win six-seven more titles for two, three more years. He's gotta get 14 more to get [the record]."
While Federer has already upset the odds with his career resurgence in the calendar year, Blake adds that age will catch up on the 19-time Grand Slam champion.
"It's tough to imagine him winning titles at 39 years old and competing with this record," Blake added.
"As much as Roger has won, the only person he'll never defeat is Father Time."