Melbourne fullback Mark Gerrard will be sidelined for four weeks with a shoulder injury suffered in the Rebels' Super Rugby loss to the Sharks.

Scans revealed grade-two damage to Gerrard's AC joint which he dislocated early in the second half of Friday night's 34-22 defeat in Melbourne.

Coach Rod McQueen said Gerrard's injury was a huge blow for the Rebels.

"It's really disappointing to be losing Mark because he's been a great contributor to the team, particularly over the last couple of games," McQueen said.

"Unfortunately, there's nothing we can do about the injury situation and we'll just have to assess the ramifications over the next couple of days."

Consistency will be key for the Rebels ahead of their clash on Friday night with Queensland after a month of contrasting performances.

Four rounds of football have delivered two impressive matches as well as two disappointing showings.

In their game against the Sharks, the "good" Rebels turned up to play at AAMI Park and came within a whisker of knocking off the unbeaten Durban side.

It was a similar performance to their shock one-point win over the Brumbies in round two.

Those games were in stark contrast from the "bad" Rebels, who were trounced by the Chiefs in round three and suffered a 43-0 defeat in their opening match against NSW.

Veteran prop Greg Somerville, who led the forwards in an impressive display against the Springbok-laden Sharks pack, said the side needed to find some consistency.

"Consistency in performance is the key thing for us," a battered Somerville said.

"That's what we need to get right.

"We have to try to not have the fluctuations in performance that we have been seeing."

Losing his pinpoint kicking game and incisive running, the Rebels attack looked rudderless for about 20 minutes.

That was when the Sharks scored two tries to regain control of the match.

"The game was there for the taking, I suppose there was a lapse of concentration and composure for about 15 minutes and that probably cost us the game," Somerville said.

Brought to you by AAP © 2024 AAP