Celtic missed a chance to extend their lead at the top of the table last night. They could only manage a 2-2 draw against Dundee United.

In many ways, even that would come as a relief, as Celtic had to come from behind to secure the draw for the Hoops. It took a second-half strike from Liam Scales to rescue a point.

While many would have hoped for Celtic to go all the way and get the win from that position, they simply could not get it done this time around.

Fortunately for Celtic, the Rangers ended up drawing their game as well. So, ultimately, the gap remained the same. But that does not mean that the club can take all of these warning signs lightly.

They simply have not gotten out of the blocks this season and have looked especially weak since that defeat to LASK. And the club have not been helped by the number of important players who are dealing with fitness issues right now.

Alistair Johnston is someone who had only returned from a spell out on the sidelines due to an injury. But the Canadian full-back only lasted 20 minutes on his return before he had to be subbed off due to a new issue.

There is mixed news in that regard. The good news is that Johnston is not out for the long term. The bad news is that he is still going to miss several games.

As reported by BBC, Martin O'Neill said regarding the fitness of Johnston: "I probably can't see him being involved before the international break, but after that, that's what they're thinking about.

"Even in the spell that he was on [the pitch on Sunday], 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."

Johnston is widely considered the starter for Celtic at right-back when fit and available. But unfortunately, he might no longer be someone that the club can rely upon for that starting role.

This is not the first time that Johnston has dealt with constant fitness issues. This has been the case for the past few years. And in professional sport, availability is the best quality. Johnston has rarely been available.

The hope is that Johnston will put his injury problems behind him. Yet, the signs are not pointing in that direction.

He is 28 years of age and has picked up numerous injuries over the past few years. It rarely gets any easier or better from here.

Colby Donovan has been starting in Johnston's absence. And he has done a decent enough job at that. There is no doubt though that Celtic have missed the Canadian international's experience and quality.