Having seen the start of his reign at Old Trafford deliver a string of positive results, the Norwegian coach was handed a three-year contract by the Red Devils.
United have suffered three defeats in their last four outings and are set to lock horns with La Liga heavyweights in the first leg of a continental quarter-final on Wednesday.
“I'm concerned by United's poor form and, if they continue to make mistakes like they have been doing recently, then, let's face it, they're going to be punished by Barcelona,” former Red Devils striker Berbatov told Betfair.
“They are making their lives difficult at the moment and it's looking tough to make the top four in the Premier League now.
“United went on that incredible undefeated run when Ole Gunnar Solskjaer took over and this is their first bad patch.
“You know, when you're winning everything feels natural and good but an important thing is knowing how to react to a defeat. I'm sure Ole knows what to do here and he will have his side fired up and ready for Barca.
“In football sometimes you have that strange thing where a club can falter against small teams but turn it on against big teams. It's crucial to get motivated for every game, not just the big ones.
“Sir Alex Ferguson sometimes didn't need to motivate us for the big games, his job and real skill was to motivate us for the small games.
“I admit, Barcelona are the rightful favourites in the tie, but, of course, so were PSG, and nothing is certain in football.
“United can forget their recent form and make a statement here, but - and it's nothing new or original - they must watch out for that man Messi.”
Ahead of a meeting with Barcelona and their mercurial Argentine captain, United have slipped to sixth in the Premier League table.
They are only two points adrift of Arsenal in fourth and three behind Tottenham in third, but the battle for Champions League qualification appears set to intensify heading into a final sprint to the finish.