MELBOURNE Heart will be sweating on scans to defender Patrick Kisnorbo after he picked up an injury in his side's 1-0 loss to Perth Glory on Sunday.
Kisnorbo went down and immediately grabbed his knee after a mistake let Glory striker Jamie Maclaren through on goal early in the second half.
Maclaren was able to beat Heart goalkeeper Andrew Redmayne on the second attempt, which proved to be the winner in front of 13,856 at nib Stadium.
Heart coach John Aloisi believes Kisnorbo's injury is not as severe as an anterior crucial ligament, but believes there may be tendon damage.
"Not 100% sure yet, he'll go have scans tomorrow," said Aloisi. "It's a little bit to do with a tendon around his knee."
Heart have already been without another of their star off-season signings, with Harry Kewell missing their last two games with whiplash.
Kewell is no certainty to play this weekend against Brisbane Roar either as he recovers from the injury suffered in round one against Melbourne Victory.
David Williams has been preferred over Nick Kalmar in Kewell's attacking midfield position and starred in their win over Central Coast Mariners but was unable to make an impact against Glory.
"We have to see how he (Kewell) is day by day and if he can get up," said Aloisi. "We'd love to have him available because he's an important player for us."
"At the moment we're putting David Williams in there but he's not really a 10. Even though he did well last week this week he didn't get much of the ball.
"You saw when he went back out wide he ended up getting in to good areas and causing problems
"We'll wait and see how Harry goes and we'll make a judgment on that later in the week. "
Heart though was boosted by the return of Michael Mifsud who made his starting debut after returning from international duty with Malta.
The 'Maltese Messi' struggled to find any clear-cut chances but Aloisi hopes when Kewell returns they can link up and develop a threatening partnership.
"We saw a glimpse of that in pre-season when Harry and Michael played together. They had a great understanding," said Aloisi.
"Harry finds great positions in that 10 role and he's very difficult to pick up.
"It's just disappointing he picked up that injury. We have to make sure we get him right because he's going to be an important player for us this season."