Roger Federer staged a stunning comeback to defeat Tennys Sandgren in their Australian Open quarter-final match on Tuesday.

The 20-time Grand Slam champion looked down and out after being a set down at the end of the third and taking a medical timeout, but he dug deep to pull-off his second five-set victory in this first Major of the year.

In a tense match, the normally ice-cool Swiss was slapped with a code warning for swearing and needed a rare medical timeout for a groin injury before winning 6-3, 2-6, 2-6, 7-6 (10/8), 6-3.

His reward is a showdown against either long-time rival and seven-time champion Novak Djokovic or big-serving Canadian Milos Raonic.

Here’s how Twitter reacted to Federer’s win: