The biggest match of Celtic's season is coming up this Thursday. Knockout European football returns to Celtic Park for the first time in three years and the test couldn't be much more difficult by UEFA Europa League standards.

Russian Premier League side FC Zenit make the long trip to Glasgow to play their first competitive match since Russian football entered its winter shutdown, but will be hot favourites for a tie that some Celtic fans are dreading as much as they are looking forward to.

There are big question marks about the Hoops ability to play at this level and to get a result Brendan Rodgers must get his team selection and tactics spot on first and foremost.

With some established stars out of form and defensive blunders numerous in recent months, selecting his starting eleven is a huge dilemma this week.

Who should he play, who should he drop, who can he rely on?

These are the THREE big selection dilemmas facing the Celtic boss...

The out-of-form Moussa Dembele or the inexperienced Odsonne Edouard?

This time last year it would an absurd suggestion to drop Moussa Dembele for any Celtic match, let alone of their most important of the season. The young Frenchman was a sensation last season, scoring over 30 goals and netting in massive matches at home and abroad. He was unstoppable.

This season couldn't be more different. Still to reach double figures in goals this term and having scored just one goal since November, there are big question marks about his importance to Brendan Rodgers' first team.

There's no denying that on his day he can be a ferocious talented, but can he be trusted to play well when it really counts?

His potential replacement Odsonne Edouard hasn't exactly been on fire this season either but at least he's shown desire and commitment to make an impression during his loan spell from Paris Saint-Germain.

A half-heart Dembele display could doom Celtic on Thursday and Brendan Rodgers has to figure out what will work best for a cohesive team performance.

Time to drop Jozo Simunovic?

Jozo Simunovic almost single-handedly destroyed Celtic's Scottish Cup hopes at the weekend, failing to deal with a Partick Thistle defence that, with no disrespect, is miles off the standard of FC Zenit's attacking line-up.

After a period of extraordinary consistency in the Hoops defensive line, Simunovic's errors have been mounting up over the last few months, to the point that supporters aren't exactly keen to see him starting anymore games.

Brendan Rodgers' problem is that with injuries in the position he isn't exactly blessed with options and would likely have to either rely on players playing out of position or youngsters like Kristoffer Ajer and Jack Hendry to form an unlikely partnership.

Celtic's failure to address their defensive problems has been ongoing for years now and it could come home to roost again at Celtic Park this Thursday.

Unleash Charly Musonda or opt for more stability?

One of the big things Brendan Rodgers must get right on Thursday is the make-up of his midfield, which plenty of options and personnel to choose from.

With possibilities of a back three and wing-backs, a packed central area or persisting with two wingers in Scott Sinclair and James Forrest with a man behind the striker, how the Hoops shape up will tell supporters about their intentions in the 90 minutes against the Russians.

Charly Musonda has been given the nod recently through the middle but playing him on Thursday could be seen as something of a risk on a night that the Hoops might need hard graft and heart more than the skills of the Belgian.

Is it time to bring Callum McGregor back into the fold? The Scottish international excelled against Bayern Munich after all.

Or is it time to simply unleash the Chelsea loanee on the big stage?