CELTIC face their most difficult opponent of the season on Thursday night as Bayer Leverkusen travel to Parkhead in the Europa League (8pm).

The Germans are flying high in the Bundesliga and sit second behind Bayern Munich after six matches.

Among their ranks is former Celtic right-back Jeremie Frimpong and the Czech Republic's Scots-torturer-in-chief Patrik Schick.

Ange Postecoglou's injury worries have extended to recent signing Josip Juranovic, while longer-term absentees including Kyogo Furuhashi remain unavailable.

Looming in the background is Sunday's trip to face Aberdeen at Pittodrie, now a must-win after another poor league result against Dundee Untied on Sunday.

Who will the manager pick to take on Leverkusen? Our writers make their predictions...

Alison McConnell

The curse of the Lennoxtown ladder strikes again.

Josip Juranovic is the latest Celtic player to find himself rubbing elbows inside a congested treatment room as Ange Postecglou looks to find a fit and available team to start against Bayer Leverkusen.

With the versatile full-back out one option is to go with the recently-sighted Liam Scales whose pace and physicality may be able to match that of former Celt Jeremie Frimpong who will return to Celtic Park just nine months after heading to Germany. Scales also has European experience given his exposure to Champions League and Europa Conference League games with Shamrock Rovers prior to his switch to Glasgow.

The biggest surprise, however, may well come with a significantly earlier than anticipated return for Callum McGregor. The Scotland international has been badly missed by Postecoglou’s side and if there is a hint that the midfielder could cope with being thrown straight back in then the suspicion is that the Greek-Australian will be tempted to gamble given the paucity of options.

READ MORE: Celtic's tough Leverkusen test: A dynamic new boss and Germany's wonderkid

Even if it was only for an hour, the game time would kick McGregor on in terms of match fitness ahead of Sunday’s trip to Pittodrie. It remains to be seen whether there is an early call taken on the fitness of the 28-year-old but his return would be a significant boost for Celtic in their bid to get back onto solid ground.

Alison's team: Hart; Ralston, Starfelt, Carter-Vickers, Scales; McGregor, Rogic, Turnbull; Jota, Ajeti, Abada.

Sean Martin

Discipline and concentration will be key to Celtic getting anything from this one.

Concentration in defence, to help minimise the risk of unforced errors that tend to plague Celtic backlines, and discipline in midfield where the energetic but rash Ismaila Soro could come in for James McCarthy if captain Callum McGregor is still not fit to start.

Josip Juranovic's unavailability coupled with Boli Bolingoli not being registered in the Europa League squad means it's a straight choice between Liam Scales and Adam Montgomery for the left-back berth. Given Ange Postecoglou has overlooked Montgomery for that position a few times already this term, I think he'll hand Scales a full debut in a real baptism of fire.

The rest of the defence in front of Joe Hart shouldn't change while, in attack, Jota and Liel Abada were the two shining lights of Sunday's 1-1 draw against Dundee United and there is little alternative to Albian Ajeti through the centre at the moment.

Sean's team: Hart; Ralston, Carter-Vickers, Starfelt, Scales; Soro, Turnbull, Rogic; Abada, Ajeti, Jota.