McGregor insists a a first victory on Spanish soil for the club could be the springboard for change.

"We need a result that's going to change the mentality," he said.

"That can be the catalyst for things moving forward.

"Performance levels in the first few games of the group have been slowly getting better.

"It's a mindset switch. We have to try and come here perform the way we want to and back that up by getting a big result."

Celtic have struggled away from home at Champions League level, recording one win in their last 16 attempts - at Anderlecht in September 2017.

Brendan Rodgers' side have spurned home leads twice in succession in the past few weeks, in the late loss to Lazio and the draw with Atletico, with the manager expressing frustration that good displays have not been rewarded with more points.

McGregor, with 20 domestic trophies to his credit, is sure the players have a determination to change that and need to expect to thrive at this level.

"There has to be a shift that when we go to the pitch that we believe and we don't want to come off that pitch until we get a result," he explained.

"We've been getting better and better but I think the biggest thing the players can take is trying to change that mentality, almost an expectation to succeed and try and get through the group.

"This is a brilliant opportunity for the players. We want to make sure it's a positive experience for us."