San Francisco 49ers head coach Jim Tomsula says nothing should be read into Jarryd Hayne spending most of the team's lopsided loss to the Pittsburgh Steelers on the sideline.

Tomsula said the 49ers wanted to test out rookie running back Mike Davis against the Steelers, but added Hayne was being looked at more as a special teams contributor.

"I wanted him playing," Tomsula, speaking of Davis, told reporters on Monday.

"We think Michael Davis is a good running back.

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"Just quite honestly, Jarryd Hayne does more on special teams and different areas for us than Michael."

With top running back Carlos Hyde suffering a bruised thigh and a head-knock in Sunday's game, back-up Reggie Bush out with a calf strain and punt-returner Bruce Ellington also hurt, Hayne was expected to play major minutes.

But, the former Australian NRL star came on for just four offensive snaps at running back and DeAndrew White was used in the second half as punt-returner in Sunday's 43-18 demolition in Pittsburgh.

Davis took 41 snaps at running back.

In last week's regular season opening win against the Minnesota Vikings the 49ers went with Hayne as Hyde's back-up and left Davis off the 46-man game day squad.

"Michael was going to play," Tomsula said.

"There was no question about that. I wanted to get Michael in the game and we have a lot of confidence in Michael."

The 49ers will attempt to regroup when they travel to Phoenix on Sunday to play one of the NFL's hottest teams, the Arizona Cardinals, who won their first two games.