Celtic full-back Alistair Johnston will be out of action until October, manager Martin O'Neill has confirmed. The Canada international, 27, went off at half-time in the second game of the season against Kilmarnock, having missed most of the last campaign with a hamstring injury. Now a scan has revealed he faces another spell on the sidelines.

"There was definitely something there, and I think the prognosis is really that it will be some time in October for him," said O'Neill prior to the Champions League play-off second leg away to LASK.

Celtic have bolstered their attacking options over the summer and been linked with a number of midfielders and O'Neill concedes the defensive area is one that needs strengthening. "If you consider that Kieran [Tierney] is essentially our only left-sided full-back, we'll have a little look," he added.

"But I really will not concentrate on anything at all until after the game, regardless of what the result is or whichever competition we happen to be in.""We've got some days before the transfer deadline [3 September], and I hope that we will get some people in."