The former striker joined the Hoops from the Norwegian outfit in 1997 and will be forever remembered in the east end of Glasgow for scoring in the 2-0 home win over St Johnstone the following season which helped clinch the Premiership title and deny Rangers 10 in a row.
Brattbakk is naturally intrigued by the battle for a play-off spot which did not go to plan, as far as Celtic were concerned, on Wednesday night.
He admitted that the Eliteserien leaders increased their chances of getting through the third qualifier but still leans towards Brendan Rodgers’ men for the second leg in Trondheim next week.
The former Norway international, these days a pilot, said: “Celtic can pull through but the task is a little bit more difficult than it was before the first game.
“I said before the game that having two games is in favour of Rosenborg because maybe they can pull a good result in Glasgow.
“Then again it is all about scoring goals and if you don’t then it is difficult to get through but my money would be on Celtic.
“If Rosenborg had lost by two goals or less I would have given them a shot of going through.
“Now, after the draw, their chances are bigger than ever. It is a good result. The result was more in favour of Rosenborg than Celtic.
“But I wouldn’t say that Rosenborg have the edge. Their chance of getting through to the next round is marginally bigger than they were before the game because I didn’t expect them to get a draw.
“I know that Celtic is a strong team, they will not come to Norway next week and lay on their backs.
“They will fight as hard as they ever can.
“The return game next week will be more open than I thought before the first game.
“Maybe nerves will play a part for next week for Celtic.
“But Celtic is the better team than Rosenborg. If they played 10 games then I would think Celtic would win seven or eight of them.”
Much of Celtic’s struggle against a side 17 games into their league season was due to the absence of a recognised centre forward.
Midfielder Tom Rogic played as a withdrawn striker to no real impact and indeed it was the visitors who created the best chances.
Leigh Griffiths was suspended and will be available for the return game at the Lerkendal Stadion if he recovers from a calf injury but Moussa Dembele’s hamstring injury could keep him out until September.
Brattbakk, who in his third spell at Rosenborg scored both goals in a 2-0 Champions League win over Celtic in 2001, believes the Scottish champions have to focus on who is available for selection.
“Those two players are obviously important to the team and make a difference if they play,” he said.
“But Celtic, with their size, should be able to replace those players without losing too much.
“However, if they use energy on players who don’t play, that is not going to take them far.
“It is about players who they actually can use.
“I would like to see both teams to go through of course but from a neutral perspective it is set for a very good game next week.
“You could talk about another draw and extra time and penalties but that is not going to happen.
“I am sure that we are going to get some goals next week.
“Whoever scores first will decide how the game goes.”