Melbourne Rebels coach Rod Macqueen admits fullback Mark Gerrard's calming effect will be missed as the Super Rugby newcomers deal with an injury crisis.

Gerrard, out for a month after injuring his shoulder in last weekend's narrow loss to the Sharks, is among a swag of sidelined players as the Rebels prepare for a test of their depth against the Queensland Reds in Brisbane on Friday night.

Lineout specialist Kevin O'Neill, a late withdrawal after aggravating a calf injury in the warm-up for the Sharks game, had an enriched blood injection on Tuesday to try to fast-track his recovery.

But he has been ruled out for the Reds clash at least.

Leading backrowers Gareth Delve and Michael Lipman face fitness tests after suffering knee injuries against the Sharks.

And another four players who were already out of action - James Hilgendorf, Hoani MacDonald, Sam Cordingley and Adam Freier - remain sidelined.

Depth was seen as a potential weakness for the Rebels in their debut season.

Macqueen said while they had stood up well so far in the face of injuries, covering the current toll made Friday's match a big challenge.

"It's going to be a good test for us to see what our depth is going to be like," he said.

Macqueen acknowledged former Wallaby Gerrard's absence was a tough blow after some impressive performances since his return from Japan.

"No team's one person and no one's irreplaceable. But Mark particularly, he's brought his personality to the side, he's a cool customer.

"He's well respected by everyone, he has a tremendous boot on him which has given us another dimension as a side.

"His coolness and experience has been great for us, so we are going to miss that."

Macqueen said the 34-32 loss to the unbeaten Sharks, after leading by as much as 12 points early in the second half, showed that the Rebels were making progress, but still had plenty to work on.

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