Swiss Indoors: Wawrinka pulls out of Federer quarterfinal with back injury

Stan Wawrinka has been forced to pull out of a dream home quarterfinal against Roger Federer at the Swiss Indoors Basel due to a back injury.

The seventh seed Wawrinka displayed plenty of grit to dispatch of Frances Tiafoe 6-3 3-6 7-5 on Thursday and was set to meet Swiss great Federer in the last-eight.

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However, Wawrinka – a losing finalist to Andy Murray at last week's European Open – will not be able to take to the court to face Federer for a 27th time.

"The bad news is that I will have to retire," he said.

"I had some trouble with my back in the last game. I'm sure I cannot make it for tomorrow [Friday]. I will pull out."

Third seed Stefanos Tsitsipas had to fight back to avoid an upset against Ricardas Berankis, the Greek recovering to seal a 6-7 (4-7) 6-2 6-4 triumph. 

Filip Krajinovic is up next after he upset fifth seed Fabio Fognini 6-2 6-4, while Roberto Bautista Agut needed three sets to defeat Richard Gasquet.

Reilly Opelka will take on the Spanish fourth seed after he recovered from a set down to defeat David Goffin 6-7 (4-7) 7-6 (7-4) 7-5.