Wallabies hooker Tatafu Polota-Nau knocked himself out as the NSW Waratahs notched a vital 28-9 victory over the Melbourne Rebels in their Super Rugby clash on Saturday night.

Polota-Nau collided heavily with the knee of Rebels fullback Julian Huxley in a tackle gone wrong in the 56th minute.

He was escorted from the field in a groggy state and the injury-ravaged Waratahs will be hoping he doesn't miss any more football through concussion.

With star playmaker Berrick Barnes having missed a large chunk of the 2011 campaign following two heavy head knocks, coach Chris Hickey said the Waratahs would monitor Polota-Nau's recovery closely.

Hickey said Polota-Nau would face a thorough medical, including head scans, on Sunday and was hopeful the big unit would be available for next week's match against the Western Force.

NSW were relieved that Barnes made a successful comeback from five weeks out, the five-eighth lasting 74 minutes before receiving a well-earned early shower.

Barnes's controlled kicking game enabled the Waratahs to dominate field position for most of a dour game played in slippery conditions at the SFS.

The Tahs also required the reliable goalkicking of fullback Kurtley Beale plus a couple of late tries to flanker Dave Dennis and lock and man-of-the-match Dean Mumm to keep the spirited Rebels at bay.

The victory ended a two-game losing run and kept the seventh-placed Waratahs in touch with the top six after 11 rounds of the competition.

"It was an important win for us," Mumm said.

"I don't think it was the most polished performance we put out this season, but it was certainly gutsy.

"There were periods in that game where we didn't really control the tempo the way we would have liked, but the pleasing thing was that we were able to pull it back onto our terms.

"The work we did early in the game, although we weren't getting much pay for it, certainly paved the way for it to open up for us in the last 20 minutes."

The visitors threatened a major boilover when they edged to within a point of NSW early in the second half with Huxley's third penalty goal.

The Waratahs were made to work hard for a 10-6 halftime advantage after encountering a Rebels outfit far more committed to the tournament debutants they trounced 43-0 in the opening match of the season.

Melbourne coach Rod Macqueen said the fact the Rebels' dressing room was a sombre one was evidence of just how far his side had come in 10 weeks since that first-round thrashing.

Polota-Nau powered over for the only try of the half in the 12th minute, with Beale converting for a 7-0 lead.

Huxley penalty goals in the 17th and 22nd minutes kept Melbourne in touch before Beale replied shortly after to give the Waratahs their tenuous four-point buffer at the break.

Beale gave the Waratahs some breathing space at 16-9 with two further penalty goals midway through the second half before Dennis crashed over in the 72nd minute and Mumm capped an outstanding captain's knock with a five-pointer on the bell.

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