Clrnc well, as Ally McCoist was saying in comms, the player surely wouldn't have gone out there without feeling he was okay. It really looked like a knee ligament injury to me, which is properly rotten luck for him on his debut and is also an absence we're going to measure in months, not weeks.
The way he went down reminded me of Bellerin going down during the Chelsea game, here's hoping it isn't as catastrophic as that was.