13 November 2019 12:07 am
Defeat by Dominic Thiem in his opening round-robin match on Sunday has left the six-time champion facing an early exit but he responded in emphatic fashion.
Berrettini was also coming off a heavy defeat by Novak Djokovic in his first appearance at the event and the 23-year-old showed why he has made such an impact this year as he pushed Federer hard in the opening set.
He saved a set point at 5-6 but Federer squeezed the accelerator to win 10 of 11 points as he cruised through the tie-break and broke to love at the start of the second.
Berrettini, the first Italian to qualify for the tournament since 1978, had three break points in the eighth game but Federer served his way out of trouble and the 38-year-old Swiss then broke to claim victory.
Incredibly, Federer is now 17-0 in second round-robin matches at the tournament but he is likely to need a victory over Djokovic on Thursday to reach the semi-finals.
Only once in his previous 16 appearances at the year-ender has Federer failed to survive the group stage, in 2008.
- Defeat by Dominic Thiem in his opening round-robin match has left the six-time champion facing an early exit
- Only once in his previous 16 appearances at the year-ender has Federer failed to survive the group stage, in 2008