Langerak, 22, signed with the German Bundesliga leaders in May last year and has been a regular in Dortmund matchday squads all campaign as the club's back-up goalkeeper.

Dortmund goalkeeping coach Teddy de Beer told westline.de that he's been thoroughly impressed by Langerak since he linked up with the North Rhine-Westphalia club.

"Mitch has developed very well in the six months, he has become more stable," de Beer said.

"Everything we were looking for, we have seen in him. Mitch has improved a lot, we have been working on his catching and his positional play.

"In one-on-one situations he has learned enormously and it's one of his strengths. He can become a good modern goalkeeper."

De Beer admitted Langerak, at 192 centimetres tall and weighing 82 kilograms, may need build muscle and use his body straight in the air in duels in the penalty area, but said he was impressed by the Australian's attitude and level of communication as a young goalkeeper.

There has been a suggestion Langerak, who hasn't had any competitive first-team game time, could play for Dortmund's second team in the fourth tier Regionalliga West in the second-half of the season.

But de Beer added if Dortmund number one Roman Weidenfeller became unavailable at some stage of the season he'd be comfortable seeing Langerak step in for the first-team.

"It does not worry us," de Beer said. "Mitch would be quite capable of replacing Roman for a while."

De Beer added Langerak has plenty of 'development potential'.