Brattbakk: In Celtic guise (CliveBrunskill/Allsport)

A first-half brace of goals from the man derided as a joke during his spell in Glasgow means Celtic require a home victory over Juventus next week - while praying that the revitalised Norwegians can take at least a point away to Porto.

However, if results go Rosenborg's way they could, in fact, leapfrog Celtic for third place in Group E and grab the UEFA Cup place at the Parkhead side's expense.

In spite of a second-half rally, Celtic's hopes were ground into the dust at the Lerkendal Stadium before half-time as Brattbakk wreaked the ultimate revenge on his former club.

An 18th-minute strike from the edge of the box followed by an opportunist finish amidst chaotic defending ten minutes from the interval condemned an out-ofsorts Celtic side to defeat before a capacity 23,000 crowd.

Indeed, only a Robert Douglas penalty save from Rosenborg midfielder Bent Skammelsrud in the 42nd minute - after Brattbakk once again tormented the Celtic defence - prevented a repeat of last week's humiliation in Portugal.

Manager O'Neill was disappointed but realistic afterwards and desperately tried to take something positive out of the dire situation.

'We got a very hard tie but I felt we played well,' he said. 'Rosenborg scored in their first attack but we were much improved in the second half.

'We had a lot of chances and were unlucky not to convert one of them. Once they got the second goal, though, it was an uphill struggle.

'We have to win next week against Juventus but Rosenborg are still in contention for third place and the UEFA Cup spot and who knows what will happen? It will be difficult. We could have taken it into our own hands tonight and it's disappointing that we didn't.'

O'Neill handed both Chris Sutton and Henrik Larsson starting slots ahead of weekend hat-trick hero John Hartson in a freezing Trondheim and Larsson came close to narrowing the deficit in the second half, forcing a superb stop from home keeper Arni Arason and heading a Didier Agathe cross against the crossbar in the 62nd minute.

It was all in vain however, despite more late pressure and Celtic must now hope for that miracle after losing their third successive away match in the group. Meanwhile, Juve booked their place in the second phase after a convincing 3-1 win over Porto.

The Portuguese took the lead in the 13th minute when Brazilian Clayton Cruz fired in a free-kick from wide on the right. Juventus drew level from their own free-kick in the 32nd minute, courtesy of Alessandro Del Piero whose shot curled into the top right-hand corner of Sergey Ovchinnikov's goal.