Loading… Roger Federer produced one of the most stunning fightbacks of his career as he booked his spot in the semi-finals, saving seven match points to beat Tennys Sandgren in five sets.Advertisement Federer, the 20-time Grand Slam champion from Switzerland, was forced off court for treatment midway through the third set, moments after failing to break Sandgren from 0-40 down – a game in which he was handed an audible obscenity code violation.When given his warning he confronted a line judge and umpire Marijana Veljovic, visibly aggravated.The true reason for the 38-year-old’s frustration soon became clear when he trudged off court for a medical timeout. When he returned, his movement was clearly inhibited as Sandgren raced into a 2-1 lead.Sandgren – the 28-year-old tennis player called Tennys from Tennessee – got tight as he approached the finish line, hitting three unforced errors as Federer saved three match points on serve at 5-4 in the fourth set.Four more came and went for Sandgren in the breaker – in which he bizarrely took a knee to his calf from a sprinting ball kid at a change of ends – and world No. 3 Federer recovered from 6-3 down to level the match.He required more treatment, this time on court, at the end of the fourth set with his upper right thigh seemingly the problem area. Promoted Content7 Of The Wealthiest Universities In The World6 Incredibly Strange Facts About Hurricanes10 Risky Jobs Some Women DoHere Are The Best Movies Since 1982 You Should Definitely SeeWhich Country Is The Most Romantic In The World?Best & Worst Celebrity Endorsed Games Ever MadePortuguese Street Artist Creates Hyper-Realistic 3D GraffitiThe Highest Paid Football Players In The WorldThe Very Last Bitcoin Will Be Mined Around 2140. Read More5 Of The World’s Most Unique Theme ParksA Soviet Shot Put Thrower’s Record Hasn’t Been Beaten To This DayWho Is The Most Powerful Woman On Earth? Read Also: Aussie Open: Nadal sacks emotional Kyrgios to hit QuarterfinalsUltimately it was to be Federer’s day, as it has been on so many occasions in the past, and he avoided the worst defeat, by ranking, during his 20 years at the Australian Open.It was the latest Houdini act from Federer – who was down 8-4 in a fifth set tiebreak against John Millman in the third round – and he will face either seven-time champion Novak Djokovic or big-serving Canadian Milos Raonic in his 15th semi-final in Melbourne.FacebookTwitterWhatsAppEmail分享 It was far from vintage Federer. He required a great deal of help from his American opponent, whose nerves got the better of him whenever he came close to securing the win, but he showed remarkable grit and determination to hang in there before winning 6-3 2-6 2-6 7-6 (10-8) 6-3 in little over three-and-a-half hours – all while struggling with injury.