THE THEMES recur when it comes to Celtic's ability – or inability – to compete with Manchester United in the Champions League. So it proved when Scott McDonald was asked what lessons he and his team-mates could learn from their 3-0 outclassing at Old Trafford in order to make a difference when the sides contest the Glasgow return on Wednesday.

"Did any of you see the West Ham game the other night?" said the Celtic striker of the 2-0 home win for the English champions in midweek. "No offence, but in the first 30 minutes of that game it could have been more than 2-0. They had class players all over the pitch and (Wayne] Rooney was still on the bench. Watch the 90 minutes of any team that have gone to Old Trafford in the past decade and beyond and see how many have won. It is very, very difficult."

Gordon Strachan chipped in by pointing out that, in the past year, United have averaged 2.8 goals in home games, making his team's beating a pretty standard one. Indeed, with two offside goals bringing up the triple for a United in "top gear", the Celtic manager claims the defeat in fact had been "blown out of all proportion". And for good measure, both he and McDonald reiterated that they were up against the best side in the world.

All of which is fine and well, but accepting that Celtic have no right to threaten United has to be set to one side as strategy is set out for the midweek encounter. Even if McDonald is entitled to his grumble about Paul Ince's – embarrassing in itself – line about Celtic being embarrassed: "The money they spent on Dimitar Berbatov, you could probably buy a whole team for that. You probably would. We've got to be realistic. People have said: what can you do to match it? Well, give us £30m and we'll see. Celtic and the like can't afford to do that and we do pretty damn well with what we've got, that's for sure. To get to the last 16 of the Champions League for two years running and win three titles in a row isn't a bad position."

Strachan might be privately cursing the Champions League predicament he finds himself in. His team are producing more fluid football than at any previous stage of his Celtic tenure. In the absence of Jan Vennegoor of Hesselink and Georgios Samaras, they have been doing so lately with pace and movement enhanced by playing all their "dwarves" who just happen to represent a band of performers Alex Ferguson's men will relish facing down.

There has been some rot peddled about Celtic's standards slipping from their previous two seasons in Europe's blue riband tournament. In reality, their performances away to United and Villarreal were more together than when they faced AC Milan and Shakhtar Donetsk on the road last year. The difference is that, in this campaign, the bar has been raised considerably. It is no coincidence that the three occasions Scottish teams have made the Champions League knock-out stages, they have nudged out a Portuguese team to finish group runners-up, rather than a side from one of Europe's top leagues.

Now, the chief objective for Celtic is to ensure they claim a UEFA Cup spot by finishing third behind United and Villarreal, with McDonald admitting they put themselves "behind the eight ball" right from the moment they opened Group E with a home draw that remains the only point they and Aalborg have gleaned. "It is a must we stay in Europe after Christmas," he said.

In the bid to do that, Strachan appreciates that, unlike with most sides, the bottom line is Celtic cannot beat United in a "square go". It means not "taking them on", yet he does not possess the sort of obdurate performers to allow them to hang tough. That has been the key to Celtic beating more accomplished sides at home over recent years. The home players have been carried along by a force of will transmitted by a hyped-up support in a stadium energised in remarkable fashion.

"We've played a lot of good teams at home in the Champions League with Milan and Barcelona but United are different," McDonald said. "They are British and when they go forward, they go direct with pace and drop off at times. Ronaldo will run 60, 70 yards at full pelt, and even Gary Neville ran 60 yards for a ball the other night. Their strikers drop off and that makes them difficult to mark and they have other players like Anderson and Nani who are starting to mature. Sometimes you see Rooney at the halfway line to collect the ball when play is further up and you're like: 'hold on a minute, why's he doing that?'. Then he'll pop a 60-yard pass diagonally and be on the end of the return.

"But it is more about what we do on the night than worrying about what they've got. If we can get in amongst them, in their faces, and have the fans behind us, a similar performance to what we had against Milan will be needed to give us a chance."

Famously, McDonald netted a late winner in that encounter. But little more than a month ago, there was a rush to reassess the worth of the £650,000 signing from Motherwell who had been gushed over following that 31-goal debut term. Debate then raged over the body shape of the squat Australian with the ample backside. It overlooked one salient fact.

"I needed games. I was out injured for three weeks (with a groin problem]," he responded coldly to the question over why he had taken until recent weeks to get his "sharpness back". "I didn't do myself any favours by playing really well against Motherwell on coming back and then disappointing in the next couple of games down to my fitness. Now I have had a run of games you are seeing the Scott McDonald of old."

The old cockiness is certainly back and that will make the striker a natural target when Celtic tackle their most important assignment of the week with a league visit to Tynecastle this afternoon.

"It can be an eye-opener (playing there] because everyone is so much closer to you, so you can hear what is going on," he said. "But it is important that you block that stuff out. It is a load of nonsense you are used to hearing week in, week out. Whether you are 20 yards or a yard away, it shouldn't be a problem."

Blocking out problems on the pitch come Wednesday will be a different matter altogether.