Ter Stegen has yet to feature in a league game for the Catalan giants - the German instead used in the Copa del Rey and the UEFA Champions League - with Claudio Bravo preferred by Luis Enrique for Spanish top-flight matches..
Real lead Barca by a point and also have a game in hand, but former Borussia Monchengladbach keeper believes Carlo Ancelotti's side can be caught.
"We have to stay focused," he told the club's official website.
"In the league we hope Madrid stumble, which they surely will do. To stay in the title race we have to keep winning our games.
"In the Spanish Cup and the Champions League, luck certainly is a factor; we have to make our own luck.
"We’ve also shown that we can be tough on defence if necessary.
"I think if we keep playing well defensively, we have a shot at succeeding in all three competitions."
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