Sharks' coach John Plumtree has defended struggling centre Frans Steyn after his indifferent start to the Super Rugby competition.  

However, the Kiwi coach said he could shift the Springbok star to fullback over the coming weeks.

Steyn has looked out of sorts in the No. 12 jersey during the opening four games of the season, with criticism mounting about his performances, especially in the side's 29-10 humbling by the Brumbies in Durban at the weekend.

"It doesn't take a brain surgeon to work out that he's not quite at his best," Plumtree said on Tuesday.

"He's a quality player and that won't just dry up and go away. I think he has a bit of work to do and he'll admit that himself. It was only two months ago the guy was at 118 kilograms. He'd comeback from a bad ankle injury and he hadn't played for months.

"Now we've got him down to 110kgs and his best fighting weight will be 105 or 106kgs."

Steyn's innocuous form has coincided with a struggling Sharks' attack that has scored just one try in their four outings thus far, while their defence was torn to shreds against the table-topping Brumbies.

They named an unchanged match 22 during their three-match unbeaten start, before making some alterations against the Australians, some partly through injury.

Plumtree's side are still without centre Tim Whitehead, who was a key backline figure last season, because of a broken arm.

"We are clearly missing a guy like Tim Whitehead in midfield. He'll be back soon and so will Frans," the coach said.

"I'm keen on playing him. He's been out of Super Rugby for a long time playing overseas for three years, so it's going to take him a little while."

Asked whether he would consider shifting the 25-year-old World Cup winner from centre to fullback, Plumtree said it could happen as soon as this weekend.

"I could if Louis Ludik's not fit on the weekend, which he might not be, then we'll possibly put him there," Plumtree said.

Ludik, who has a shoulder injury, was one of three players with an injury cloud hanging over their heads ahead of the clash against the Rebels.

Springbok prop Jannie du Plessis has a thigh problem, while lock Anton Bresler (shoulder) is also doubtful.

All three have not taken part in training this week, although they might participate in some sessions closer to the game.

SAPA