Swiss tennis great Roger Federer said he was in a "race against time" to be fit for the Australian Open as his recovery from two rounds of knee surgery takes longer than expected.

Federer, 39, has been out of action since February, when he underwent keyhole surgery on his right knee. In June, Federer revealed a follow-up operation and called off his 2020 season. But despite months of rehabilitation, the 20-time Grand Slam champion said he was still not "100 per cent" for the Australian Open, which looks likely to be delayed from January to February over Coronavirus restrictions.