Muscat was sent off late in Saturday's 2-2 draw after a high challenge on Zahra, which forced the Heart flyer off the pitch with a knee injury.

After the game, van 't Schip was asked if there was any excuse for such a tackle.

"I don't think so but it happened," he said. "What can you do?

"It doesn't fit on a football field a tackle like that. Hopefully it's not going to end a young career of a great player."

Van 't Schip added: "Adrian is not looking good. The tackle was terrible.

"Hopefully he will recover and will come back, but it's not looking good."

The Heart boss also said he felt his side dominated the clash and should have taken all three points.

"In the second-half there was only one team playing," he said. "We really needed the win, we knew it.

"The win was not in the scoreboard but in every other aspect we were surely the winner of the game. For the moral of the team and the proud fans it was a great performance."

Sixth-placed Heart's next match is away to Brisbane Roar on Saturday.

* Heart confirmed, Zahra would undergo scans on Sunday to assess the full extent of the injury, but an immediate review suggests his season is over due to ligament damage in his right knee.