Manchester United Treble winner Denis Irwin says Erik ten Hag's team can make a massive stride in their development by defeating Barcelona in their Europa League playoff.
Irwin reckons his old side could lay down a marker by beating Barcelona this week.
He told the club's official media: "You're coming up against one of the big boys who are doing very well in the local league, La Liga.
"[A win] sends a huge message to our fans and to everybody out there because we've had a couple of difficult seasons.
There's been huge progress this season and that would rubber stamp the direction we are going in.
"I think for the confidence of the playing staff, the manager, the fans, it will be a huge plus for us, it really would."
Irwin believes his old side will have "defend as a unit" if they are to stop Robert Lewandowski on Thursday night.
On Lewandowski, he told the club's website: "He's doing it again at Barcelona and playing very well.
"He's got great experience - he's one of those players that it doesn't matter what age, he will always score goals.
"Our defenders, particularly the two centre-halves, will have to be on their toes.
"But Barcelona as a whole are a great attacking team, they score plenty of goals. Whoever plays in that defence will have to play as a unit and make sure that we don't concede too many chances."