Johnston felt something again, says O'Neill
· Yahoo Sports
Celtic manager Martin O'Neill explained Alistair Johnston "felt something again" after his substitute appearance in the win over Hibernian was cut short.
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The Canada right-back, 28, missed most of last season with hamstring issues and had been absent since early August with a recurrence of the injury.
His appearance off the bench at Easter Road in Celtic's 2-1 victory lasted 21 minutes.
"We're not sure just at this moment," O'Neill told BBC Scotland.
"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.
"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."
More positively for O'Neill, central defender Cameron Carter-Vickers came through the final 17 minutes after taking over from Johnston. The United States defender had been missing since mid-September.
"Of course, we need every single body back," O'Neill said.
"He seems to have come through the game OK. Delighted that the big players are back."
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'In the circumstances, best win of season'
Camilo Duran's winner followed Jason Kerr's own leveller as Celtic bounced back from Thursday's 2-1 home Europa League defeat by Celta Vigo.
A ninth Scottish Premiership win out of 10, victory at Easter Road restored Celtic's four-point lead at the top of the division. Dundee United visit Celtic Park on Wednesday, with three more fixtures to come before the next international break.
"Absolutely delighted with it," O'Neill said.
"Considering the circumstances, considering the conditions today and considering what has happened on Thursday [losing to Celta Vigo], 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.
"Thankfully, we did score so quickly afterwards [the Hibs goal] and we got the winning goal. It's a difficult afternoon even in good conditions form. I always find Easter Road really difficult."