Roger Federer beat Matteo Berrettini in straight sets this afternoon to keep his ATP Finals hopes alive.
The Swiss star was beaten by Dominic Thiem in his first round robin match but he still has a chance to get out of the group stages.
To do so, the 20-time Grand Slam winner will likely need to beat world No 1 Novak Djokovic on Thursday.
And Greg Rusedski has warned Federer to find another gear if he is to get one over his Serbian rival.
“He will be pleased overall with his performance but it felt like he was only playing at 80 per cent of his ability,” Rusedski said of Federer on Amazon Prime.
“In his next match against Novak Djokovic he is going to have to step up his level if he is going to qualify for the semi-finals.
“He is going to have to find a way to raise his game but all the pressure will be on Novak.
“He is trying to be world No 1 and Djokovic can sometimes feel the pressure.
“When Roger is loose and with no expectation he plays his best tennis so I expect a really higher level from Roger Federer in that match-up.”
Federer took a day off between his matches against Thiem and Berrettini to get over his opening defeat.
And fellow pundit Daniela Hantuchova saw some improvements from the world No 3 as he got his campaign off the mark in London.
“I thought the movement was much better from Roger,” she said.
“He wasn’t serving too badly against Dominic but today he was going more for his target.
“He was much more effective and also he was trying to come in [to the net] more.”