Novak Djokovic says he “suffered a lot” during a hard-fought victory over fellow veteran Marin Cilic in the second round of the Shanghai Masters.

The 38-year-old Serb, playing in his first first tournament since the US Open and his first non-Grand Slam match since May, clinched a 7-6 (7-2) 6-4 win in one hour and 54 minutes over his 37-year-old opponent.

The combined age of Djokovic and Cilic – 75 years and 139 days – was the oldest ever between two opponents in an ATP Masters 1000 main draw match.

Little could separate the pair in the first set as both players held their serve before Djokovic took the tie-break.

Cilic’s serve was then broken in the third game of the second set and world number five Djokovic managed to hold his own to secure his spot in the third round.

Djokovic acknowledged he had to “fire up all engines” to beat Croatia’s Cilic in a grueling encounter at the Qizhong Forest Sports City Arena.

Djokovic will face big-serving German qualifier Yannick Hanfmann in the third round.

Sixth seed Ben Shelton looked rusty as he lost 6-2 6-4 to David Goffin of Belgium.