The goalkeeper hopes his former team-mate can overcome two difficult seasons to hit the heights again in 2014-15, and is keeping his fingers crossed over another key colleague
Kagawa found himself marginalised at Old Trafford under David Moyes last season and his future remains uncertain following Louis van Gaal's arrival at the club.
The Japan international and Mexico striker Javier Hernandez have been tipped to become the first casualties of the Dutch coach's tenure, with Atletico Madrid reportedly interested in the attacking duo.
Heavy competition for a playmaking role with Wayne Rooney and Juan Mata looks likely to cost Kagawa the chance to prove himself for the Red Devils.
Nevertheless, his former Borussia Dortmund team-mate Langerak insisted the 25-year-old has what it takes to recapture the form he showed in the Bundesliga.
"He's scored goals in the Premier League, he's made assists," Langerak told Goal Australia.
"(He) just (needs) a chance to settle into his role. Once he gets a few goals and people get adjusted to the way he does things then he'll be fine."
"I know how good he is. We were all surprised that he didn't play so much this year. But it doesn't mean he's not a good player and doesn't mean that he hasn't progressed. Because for sure, he's absolute world class."
Should Van Gaal opt to keep Kagawa, Langerak believes the Netherlands' World Cup coach can get the best out of the former Cerezo Osaka star.
"Honestly, I think so," he said.
"I think he'll really take his game to the next level."
As for Dortmund, key defender Mats Hummels has been heavily linked with United during the close-season, although recent reports have claimed the Premier League side are reluctant to meet BVB's asking price for the World Cup winner.
Speaking ahead Germany's triumph in Brazil, Langerak was hopeful his team-mate would resist the advances of Europe's biggest clubs.
"He hasn't said anything to me," he said.
"I am very good friends with him. As far as I know he'll definitely be staying, he'll probably be extending his contract.
"The good players from our club always get linked. Marco Reus, (Robert) Lewandowski, Mats Hummels.
"All the top players are always getting linked with elsewhere but it says a lot when they do stay and when they do extend their contract. That's enough (of a) message in itself.
"When clubs like Real Madrid and Barcelona come knocking, players are going to notice. But if they still make the decision to stay in Dortmund, that's a massive plus."