Leigh Griffiths vital for Celtic against Astana - Kris Commons

Celtic's Leigh Griffiths scored against Astana a year ago

Leigh Griffiths' participation is crucial to Celtic's hopes of a healthy first-leg lead against Astana on Wednesday, says Kris Commons.

The former Celtic midfielder predicts a 2-0 or 3-1 defeat for the Kazakhstan visitors - but only if the Scotland striker is fit enough to play a part.

"I think they will struggle with the scoring side of things," Commons said of the prospect of him missing out.

"If Griffiths is fit, 2-0 or 3-1. I think they'll score plenty of goals."

Celtic host the first leg of the Champions League play-off - just over a year since beating the same opponents 3-2 on aggregate on their way to qualifying for the group stage.

Griffiths scored in both legs but has been struggling with injury and came off the bench again in Friday's win over Partick Thistle.

With fellow striker Moussa Dembele still sidelined through injury, manager Brendan Rodgers has tried midfielder Tom Rogic and wingers Scott Sinclair and James Forrest up front.

Patrick Roberts was a successful stand-in while the Manchester City winger was on loan last season and Celtic are trying to secure his services again.

"I'd love to see Paddy Roberts up there," Commons told BBC Scotland when asked who his preference would be if Griffiths was not available.

"I'd probably say James Forrest just because of his willingness and eagerness to run in behind.

"I think he can stretch teams that will give space to the likes of Sinclair, Rogic and Stuart Armstrong.

Kris Commons scored for Celtic against Shakhter Karagandy in 2013

"Brendan knows how vital are these two games. If Leigh Griffiths is 80% fit, let's keep him on the bench and let's try to get him up to 90-95 and give him a realistic chance of leading the line and scoring goals.

"I think he's got a blend of good attacking players, but as a focal point in these big games, you need a proper number nine and Leigh Griffiths is your number nine."

Commons has concerns about Celtic's central defence in the absence of injured pair Dedryck Boyata and Erik Sviatchenko.

Asked if he thought Nir Bitton, the Israel midfielder who has been drafted into the position, had proven to be a good stand-in, Commons replied: "In possession, yes, but over two games, they are going to have to defend."

Commons was on the wrong end of a 2-0 defeat at Astana Arena against Shakhter Karagandy in 2013 before Celtic progressed after a three-goal win in the home leg.

"Obviously there's the heat, the different time zone, the travelling, but for now the emphasis will be on trying to take a generous lead over there," he suggested.

"I think the home tie will be crucial. The emphasis is going to be on Celtic getting a good start, dominating possession and trying to create as many chances as possible.

"You want to be going over to Kazakhstan with a generous lead to make that night a little more comfortable, but there is no question it is going to be a very difficult fixture.

"Looking at the players they've got, Celtic should have enough to get through this tie."