CELTIC right-back Alistair Johnston faces weeks rather than months out following his latest hamstring injury.

The Canada international missed the bulk of last season with a hamstring problem and suffered a similar injury in August.

Johnston only made his comeback off the bench in Sunday’s win over Hibernian but lasted just 21 minutes before breaking down.

Manager Martin O’Neill said: 'He got a scan and it’s not too bad. It’s not the same injury.

'I think there’s three muscles in the hamstring and it’s one of those, but shorter term for him.'

The 28-year-old is set to miss games against Dundee United, Falkirk, Besiktas and Kilmarnock but should return after the international break.

'I probably can’t see him involved before the international break, but after that there, that’s what they’re thinking about,' O’Neill said.

'Even in the spell that he was on, he looked commanding, he looked a real player.

'But he’s very philosophical about it all, he’s taking it in his stride and I think he’s really happy with what the scan has shown.'

Meanwhile, Colby Donovan insists he will maintain the single-minded determination to be a Celtic first-team player that has driven him since joining the club aged six despite getting the comfort of an extended contract.

The right-back this week signed an extension which committed his future to Celtic until the summer of 2031 after making 44 first-team appearances.

The first person the 20-year-old told about his new contract was fellow full-back and Celtic fan Kieran Tierney.

'He was a big role model for the boys in the academy when I was younger growing up,' said Donovan, who will be fit for Wednesday’s visit of Dundee United after going off injured against Hibernian on Sunday.

'Now I’m playing with him and I’m a good mate with him as well, so it’s mad. But there’s no better person to look up to than KT. I’m loving learning from him every day and he’s at the top of his game.

'When I was younger, it was just his determination to give everything for the badge, so that’s what I see in his game even now as well, he gives everything for the club.

'So that’s what I try to put into my game. You might not be having the best of days but you just need to give everything for the club and for the boys, don’t you?'

Donovan’s interactions with Tierney and other team-mates including James Forrest and Callum McGregor began in his school days.

'I remember I actually got a photo of KT, I’ll need to find it somewhere, but I was telling him about that the other day,' he said.

'And you had Cal, James, sometimes they’d come down to Barrowfield and talk to the young players and that was such a good thing for the young players, seeing that it is possible to come through at a big club like this.

'When you see them doing it and, obviously I’m doing all right for myself just now, I just hope the academy players are looking up to me as well.

'Since I was a young boy I was always focused on playing for Celtic and even about two years ago it was just football, it was always football.

'So when I made my debut at Celtic, it was a dream come true. It’s one of the things I wanted to do most when I was younger.'

Johnston’s injury means Donovan is likely to start regularly until the international break, when he hopes to be in the Scotland squad again.

But his obvious enthusiasm for playing for Celtic makes it highly unlikely he will take his first-team place for granted.

'You know how hard it is to come through as a young player,' he said. 'Sometimes you’ll get your opportunity and maybe it’ll never happen again.

'It’s about taking that chance and not looking back and that’s what I’ve been doing. I’m still doing that now. You’re never destined a place at Celtic.

'It’s such a big club, you’re expected to win every game so I just try and do everything that I can for the club and for my team-mates and hopefully put on a good performance.'