Australian Langerak joined Dortmund in 2010, but has had to largely play back-up to 34-year-old Roman Weidenfeller.
However, Dortmund's horrible start to the Bundesliga season - which has seen them, at times, sit bottom - resulted in Weidenfeller being dropped.
Langerak has started Dortmund's last two matches, a 1-0 Bundesliga success against Hoffenheim and Tuesday's 1-1 UEFA Champions League draw with Anderlecht - a result that ensured Jurgen Klopp's side topped Group D in Europe's premier club competition.
Talk of a changing of the guard at Dortmund has followed Klopp's decision to replace Weidenfeller with the 26-year-old.
But ahead of another crunch league clash for 14th-placed Dortmund, against a side below them on goal difference only, Langerak is unsure if he will start again.
"I'm not sure how things are going to go in the future," Langerak told the Bundesliga's official website.
"All I can do is to keep training and working, and when I get the chance to play, take it with two hands.
"I wouldn't say that [I am the number one goalkeeper] until I play 40 or 50 games in a row…until then, Roman's the number one and I just have to keep training.
"If I get the chance to play at the weekend then great, but obviously I've not spoken to the head coach about that, so I'm not too sure.
"In the Bundesliga we need to continue to collect points. We haven't had the best season so far in the Bundesliga, so points on the road would be important.
"Against Hertha, I think we need to definitely get the three points to haul ourselves a little bit further up the table."
Langerak's clean sheet in the Hoffenheim win that dragged Dortmund off the bottom and out of the relegation zone means he is likely to start in goal again.
And given the tight nature of the bottom half of the Bundesliga table, Dortmund could rise as high as 10th if they win in the German capital and other results go their way.
Dortmund's next three matches - which come in just over a week before the mid-season break - shape as a crucial period of the campaign.
Only one player, Pierre-Emerick Aubameyang (four goals), has netted more than three times for the German giants in the league this season.
Klopp - who looks set to be without Marco Reus (ankle), Sokratis Papastathopoulos (leg) and Ji Dong-won (thigh) - undoubtedly needs more from his forwards.
Hertha's season has also been poor and they sit 15th with just four wins.
Only two sides - Werder Bremen and Stuttgart - have conceded more than their 26 goals, and although Salomon Kalou looms as a danger man for Hertha, his impact could be rendered useless if his side struggle at the back again. Hertha have not kept a clean sheet in five matches.
Hertha, though, do have a good record against Dortmund in recent years - winning 2-1 on both of their last two trips to Signal Iduna Park.
Dortmund have won three of their last four matches in the German capital, however, including a 4-0 success in May that saw now-Bayern Munich forward Robert Lewandowski score twice.
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