Melbourne are confident key Rebels Stirling Mortlock and Mark Gerrard will be available for their crunch Super Rugby match against the NSW Waratahs next Saturday night.

The Waratahs dished up the Rebels' worst loss of their debut season, 43-0, in round one played in Melbourne.

Since then the Rebels have won three games and proven competitive in most, but the NSW match marks the start of the toughest period in the side's short history.

Melbourne travel to Sydney then host the rampant Queensland Reds before two games in South Africa.

"Don't remind me," coach Rod Macqueen joked when asked about the looming games.

The Rebels lost Mark Gerrard before their 40-23 loss to the Auckland Blues at North Harbour Stadium on Friday night after he injured his hamstring at their final training run.

Skipper Mortlock, who missed the previous round with a hip injury, left the playing field midway through the second half with back tightness.

But Melbourne were hopeful both would be available next weekend.

"We are confident that Stirling will be available for the Waratahs game," a club spokesman said on Saturday after the team returned to Melbourne.

"Mark Gerrard will be monitored during the week but we are hopeful that he will be right to play as well.

The late withdrawals of Mortlock and then Gerrard meant Melbourne have been unable to field their preferred centre combination in either of the past two games which Macqueen said was unsettling for the side.

Their defence was particularly disappointing early on, with mercurial five-eighth Danny Cipriani, defending in the centres, contributing to two early tries scored by the Blues when he rushed up out of the line.

But the Rebels fought back to within five points until two tries by the home side in the final 10 minutes.

"There was certainly some good things there and when we put it together we've got good shape and we're a much better side," Macqueen said.

"We're agood team with the ball, we've just got to be able to get it more often and keep our penalties down."

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