EUROPEAN football after Christmas is the sort of pleasure which could come with a government health warning.

When they host Inter Milan tomorrow night the 60,000 sell-out crowd alone will confirm it as Celtic's biggest game of the season so far. Ronny Deila, John Collins and some of their newer players are about to experience the campaign's first truly magical European night in Glasgow's east end. Was it grander occasion than the Old Firm League Cup semi-final? "This is bigger than the Rangers game, without a shadow of a doubt," said Collins.

But this isn't a night at the theatre or the movies: the vast audience knows there is a risk of being made to suffer. Celtic are in far better shape now than when finishing their successful Europa League group campaign in December, when two closing defeats brought a flat end to their progress to the final 32. Buoyant form in the SPFL Premiership, Scottish Cup and League Cup has put a spring in their step since then but Inter, their famous old adversaries from Lisbon in 1967, have the capacity to rattle Celtic and sober them up. The word Collins used was punish. The sort of casual play Celtic might get away with in domestic games will, if repeated in this first leg, be punished.

"This is a massive step up from the SPFL, no disrespect to these teams," he said. "This Inter team is full of international players worth a fortune, on huge salaries, and if we make mistakes or switch off against this type of opponent, they'll create a chance or score a goal. That's the reality. In the SPFL, you can make a mistake or give the ball away and they don't punish you. Here we will be punished and we will have to be switched on for the full 90 minutes. The top teams try to stretch you and play through you, so it's important that we stay nice and compact. Earlier in the campaign we weren't as sharp, we weren't as switched on as we should have been and we got punished. We know that. Hopefully we have learned our lessons. For months down the line we've had lots and lots of training sessions, lots of games to try to correct our weaknesses. We're certainly not perfect but we're in a better place now than we were at the last European tie."

No country has won more Europa League/UEFA Cup finals than Italy and no club has won it more than Inter Milan (whose three triumphs are matched by Juventus, Liverpool and Sevilla). Some of the bigger clubs has lost a little interest in the competition in recent seasons before Uefa rekindled their enthusiasm by granting its winners automatic entry to next season's Champions League. For a force like Inter, currently tenth in the league when only the top three Italians finishers qualify for the elite tournament, winning the Europa League may offer a more realistic route. "I think all teams will be taking it unbelievably seriously now because you get access to the Champions League if you win it," said Collins. "A fantastic move by Uefa. That changes the mindset of every team that's in the tournament now. Inter will now think this is their route to the Champions League. They will be doing everything possible to get a result."

There was no dramatic improvement in form when Roberto Mancini arrived as manager in November, but this month has given them encouragement. "Their last two results [3-0 v Palermo and 4-1 v Atalanta] tell you they are a team which is progressing and developing. They have a new manager in and sometimes it takes a little while for a manager's ideas and principles to bed in. They are obviously heading in the right direction. They'll be coming with more confidence - victories and scoring goals breeds that - so it is going to be a tough game. We know that.

"Mauro Icardi is the one who scores the goals but they've good players in midfield as well. Fredy Guarin, the Colombian midfielder, scored a couple at the weekend from outside the box. One right, one left foot, so we will be aware of their individual talents. We are at home and are at our best when we are on the front foot and pressing our opponent, trying to control the game with possession. But we have to be realistic - we are up against a quality opponent. This is not the SPFL so they will have possession of the ball. But our attitude is that we are at home so we have to start the game well and take it to our opponents."

Collins played in the Monaco side beaten 3-2 on aggregate by Inter in the 1997 Uefa Cup semi-final. The Italians had been "lucky" he joked yesterday. There was another gag when he was asked about Inter being offered Rangers' Murray Park complex to train. "It's a good venue. It's a good choice. I'm sure everyone at Murray Park will be desperate for a good Scottish victory." Maybe not, but there will be no shortage of support washing down on them from Parkhead's vertiginous stands.