Martin O'Neill said Alistair Johnston "felt something again" after his substitute appearance in Celtic's 2-1 win over Hibernian at Easter Road was cut short. The result was Celtic's ninth Scottish Premiership win from 10 and restored their four-point lead at the top of the division.
Johnston set for a scan
Johnston's appearance off the bench at Easter Road lasted 21 minutes. O'Neill said: "We're not sure just at this moment."
He added: "When you've had a couple of hamstring problems, I think that your concern is anything you might feel is a bit of a niggle."
On the next step, O'Neill said: "I don't know. He's not sure, neither is the doctor at this minute. He'll obviously need a scan and we'll see how he is."
Johnston had missed most of last season with hamstring issues and had been absent since early August with a recurrence of the injury.
Carter-Vickers returns
Cameron Carter-Vickers came on for the final 17 minutes after taking over from Johnston. O'Neill said: "He seems to have come through the game OK. Delighted that the big players are back."
The United States defender had been missing since mid-September. O'Neill also said: "Of course, we need every single body back."
Celtic take the points at Easter Road
Camilo Duran's winner followed Jason Kerr's own leveller as Celtic won 2-1 at Hibernian. O'Neill said: "Considering the circumstances, considering the conditions today and considering what has happened on Thursday , I thought this was our best win of the season and we didn't play particularly well in the game. It was even better than last Sunday."
He added: "Thankfully, we did score so quickly afterwards and we got the winning goal. It's a difficult afternoon even in good conditions form. I always find Easter Road really difficult."