Aptly named rank outsider Tennys Sandgren ensured Stan Wawrinka's comeback from injury lasted just two matches by pulling off a second-round Australian Open shock.

Sandgren moved into the top 100 in the rankings for the first time last year and could make further strides in 2018 on the evidence of a 6-2 6-1 6-4 defeat of ninth seed Wawrinka on Margaret Court Arena.

Three-time grand slam champion Wawrinka underwent knee surgery after a first-round loss at Wimbledon, cutting short his 2017, and revealed he was still experiencing discomfort following a victory over Ricardas Berankis on Tuesday.

The 2014 champion was unable to live with 97-ranked American, who had never won a grand-slam singles match before this week but can now look forward to facing Maximilian Marterer, who shocked Fernando Verdasco, in round three.

Sandgren, ranked as low as 330 in 2016, struck 31 winners and broke five times, with Wawrinka unable to break the 26-year-old solid server from Tennessee as he was brushed aside in straight sets.

It was the first victory over a top-10 opponent for Sandgren, who blasted down 11 aces in the biggest win of his career. The first major of the year appeared to come too soon for Wawrinka.