Williams, seeking to equal the all-time record for majors, raced away with the first set but lost 1-6 6-3 6-3 to the inspired former world number one. The American called on the trainer for an Achilles problem early in the third set and struggled physically from then. Belarusian Azarenka faces Japan’s 2018 champion Naomi Osaka in the final. Two-time Australian Open champion Azarenka had been appearing in her first Grand Slam semi-final since 2013 after troubled times on and off the court. But she has been in fantastic form in recent weeks, having now won 11 matches in a row after victory in the Western & Southern Open just before the US Open. Williams and Azarenka were once regular opponents on the biggest stages – but this was their first encounter in the latter stages of a Grand Slam since a Wimbledon quarter-final in 2015. The two good friends have had maternity leaves since then and Azarenka’s career was also stalled by a lengthy custody battle over her son. Williams had dominated their head-to-heads, winning 18 of their 22 encounters until now, including back-to-back wins in the 2012 and 2013 US Open finals. And until now she had won all 10 of their Grand Slam matches. But that record was from a different time – in this match the stakes had changed, and so had the players. Williams has for some time been carrying the pressure of the personal desire and the public expectation of a matching Margaret Court’s titles, while Azarenka is playing with a new freedom that has come only recently since she admitted she was finally enjoying her sport having “taken the fear of failing away”.