Mitch Marsh suffers groin strain in SA

Australia have a fresh injury concern on the tour of South Africa, with Mitch Marsh suffering a groin strain in the second Test loss.

Mitch Marsh has been Australia's best performer in South Africa but may miss the third Test. (AAP)

Mitch Marsh has suffered a groin strain in Port Elizabeth, with the allrounder now racing the clock to be fit for Australia's third Test against South Africa.

Marsh has been the tourists' best performer so far in the four-Test series, snaring a couple of key wickets and producing a match-winning knock of 96 in Durban.

"He's got a bit of a groin strain, so he was struggling to move a little bit," Steve Smith said.

"We'll wait and see."

The four-Test series continues in Cape Town on Thursday week.

Smith suggested Marsh's setback is the only injury concern, with Mitchell Starc, Josh Hazlewood and Pat Cummins all fit and firing.

"All the quicks are going really well," he said.