REALISM is a quality which separates dreamers from doers. If Celtic are to do anything in this season's Champions League, they have to get real to the shortcomings which threaten to undermine the very basics of their burgeoning game plan.

Before a tie can be won, at home or away, a goal has to be scored. And, if even a point is to be secured, the back door has to stay firmly closed.

The worrying problem for Gordon Strachan's side at the moment is they fall between the two stools of wanting to hurt the opposition while also defending themselves against any pain.

With the pace now injected into their armoury, they will always have a puncher's chance of delivering a knockout blow in one of these Champions League catch-weight contests against the likes of Villarreal or Manchester United.

But there will also be long periods when the high amounts of energy expended will tell -even for a side as fit as Celtic - and they will be pushed back on to the ropes.

That's when tired minds and legs lead to mistakes and the blow to the solar plexus is most likely to be unloaded, on Tuesday from the boot of Marcos Senna after 66 minutes of slugging it out.

So, what to do? Revert back to the tried and too-often failed tactics of playing on the back foot, holding in the clinches and maintaining a stiff defence while hoping to get a free shot from a set-piece?

Or push on with the more progressive fast counter-punching game which, if executed correctly, can cause opponents to hold back for fear of being caught unawares?

Fortune is supposed to favour the brave, though there are more than enough examples in the history of the Champions League to counter that particular theory.

Given the precarious position Celtic now find themselves in after round two of this scheduled six-rounder to see who qualifies for the knockout stages, going for it is surely the policy which most supporters would welcome.

However, if that led to elimination from Europe altogether, allowing the lightweights from Aalborg to slip in to take the Uefa Cup consolation prize handed to the team finishing third in the group, would those same fans stand and applaud the have-a-go-heroes?

A run in the competition soon to be renamed the Europa Cup could work wonders not only for Celtic's falling co-efficient, but also remind them how to win on the road, something they achieved in some style at places like Blackburn and Liverpool when their poor Champions League away record was still in its formative years.

Of course, it is premature to even speak of failure to make it three Last 16s in a row.

And, if the glimpses from Villarreal of what the newly fashioned 4-5-1 formation can offer develop significantly, all hope is not yet lost.

However, the ease with which Villarreal advanced down the wings lit up like a neon sign the downside of having pacey, attack-minded players in the key wide midfield positions.

For all Shaun Maloney, Aiden McGeady and, when moved out there from his central position, Shunsuke Nakamura can bring to the party when Celtic are in possession, what they lack when asked to protect their full-backs at this level of the game is - or, at least should be - of genuine concern.

Strachan was only half joking when he said ahead of Tuesday's game that he believed he had the players who could get goals through their pace, but that it might need to be four to get a result.

Maybe that's playing football the fabled Celtic Way', but is it what is required to progress in the Champions League?

And is there enough patience within the club and its supporters to allow the time to find out? If it goes wrong at a place like Old Trafford, the consequences could be severe.

But if the game in Villarreal proved nothing else, it confirmed it can at least give Celtic a fighting chance of pulling off a shock, even against a side as accomplished as the La Liga leaders.

Strachan has the final call whether he sticks or reverts to old school style when they head to Manchester on October 21.

If he canvasses the players who had to try and execute the game plan in Spain, the indications are they will vote to give it another go rather than sit back in an ultra-defensive formation inviting Ronaldo, Rooney, Berbatov and Co. to try and pick them off. Maloney - a man renowned for being self-critical - was not content with how he operated in this line up against Villarreal, but was far from dismissive of the way the team in general executed the game plan.

He said: "The performance was pretty good, but the overall reaction is just disappointment.

"In the second half Villarreal were the better team. At half- time we were not told to sit back. But I think they stepped it up a gear.

"I know that down the flanks, especially on my side, the right back pushed right on.

"They gave us a hard time, and in the second half they kept the ball a lot better than us."

That is such a key factor in any game at this level, but especially in one whereby the very nature of your tactics you will have to work so hard.

As any player will tell you, running with the ball is so much easier than chasing an opponent who has got it.

Against a side who only two years ago were contesting the semi-finals of this competition, and who have already done what Celtic need to do now -take something from Ol d Trafford - working hard for the entire 90 minutes is the minimum you will be asked of every player.

That effort will seem as nothing in the matches which lie ahead because the battle for European survival is about to begin in earnest. Belief can act as fuel, and that appears to have received a boost with the positives taken from the opening hour in Villarreal.

But Celtic may require to be turbo-charged to keep up with Manchester United who rocketed to the top of the group with their 3-0 win in Aalborg, which not only highlighted how good a side the current holders are, but how devoid the Danes are when it comes to penetrating defences.

Then again, like United and Villarreal, Bruce Rioch's side can claim to have taken something from an away game in Group E.

Over to you, Celtic.