'That's bizarre, I've never seen Sam do that in his career'

Sam Groth left commentators stunned with a bizarre outburst in his mixed doubles semi-final loss alongside compatriot Sam Stosur.

The big-hitting Aussie completely lost his serve in the early stages of the match, at one stage yelling out after double faulting.

"What is going on with my second serve!?" he loudly questioned his players' box.

Groth and Stosur in action on Friday. Image: Getty

Aussie tennis greats Rennae Stubbs and John Fitzgerald were rather taken aback in commentary.

"There's nothing anyone can do but you," Stubbs laughed.

"That is quite bizarre to see Sam do that," added Fitzgerald.

"I've never seen it in his career, it looks like he's completely lost his confidence.

The Aussie pair fell one match short of the final, losing to Sania Mirza and Ivan Dodig 4-6, 6-2, 5-10 (super tiebreak).

Mirza and Dodig will meet American Abigail Spears and Colombia's Juan Sebastian Cabal in the final.

Spears and Cabal accounted for Ukraine's Elina Svitolina and Australian Chris Guccione in straight sets.

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