Dundee United's Gary Mackay-Steven could require surgery
Dundee United winger Gary Mackay-Steven is facing up to six weeks out of action through injury.
The 21-year-old, who withdrew from the Scotland Under-21 squad in midweek, sat out United's 3-0 Dundee derby win.
When asked about the knee injury, manager Peter Houston told BBC Scotland: "At half past eight tomorrow morning, he is speaking to a surgeon.
"They might not need to operate. If they need to operate, it is four to six weeks."
Houston was still hopeful that a bit of rest will resolve the problem rather than surgery being necessary.
"Hopefully, it is not and it can settle down," he said.
"He has got a bit of flaking on his cartilage or something like that. He has got bone bruising."
Houston agreed with Hearts counterpart John McGlynn, who called for protection of flair players after winger David Templeton was sent off for retaliation in last weekend's 1-1 Edinburgh derby draw against Hibernian.
"He's had a few kicks so far this season in the few matches that we've played and he's a young talented player and he goes past people and opposition managers are probably saying 'look after him'," said the United manager, suggesting that Mackay-Steven had become a marked man.
"We need protection. I heard John McGlynn talking about protection for skilful players. I echo his words."
Houston stopped short of suggesting that challenges from opposition players required red cards but pointed to the treatment meted out by Dinamo Moscow in the two legs of United's Europa League qualifying defeat.
"They are just hard and a few people have been booked, even the Russians as well had a couple of guys booked for fouls on him," he added.
"A couple, not just one, of the Russians kicked him over there as well and brought him down when he got away from them."
Unless Mackay-Steven is given the green light to return to action, United could be without for two of their best performers this season when they visit Kilmarnock next weekend.
Johnny Russell was sent off after scoring twice against Dundee and is in line for a two-match suspension unless United are successful with a planned appeal against referee Calum Murray's decision.