The 22-year-old goalkeeper refused to mention the Blaugrana by name but says that he will be playing for "a very special club" next season
The 22-year-old goalkeeper rejected a new contract from Gladbach in January, with Saturday's 3-1 defeat to Wolfsburg likely to be his last appearance for the club, and is widely tipped to replace the outgoing Victor Valdes at Camp Nou.
The Germany international has refused to name any club specifically but delivered a series of thinly veiled hints that he will soon be a Blaugrana player.
"I've got a new club and I'm learning Spanish," he told German broadcaster ZDF in an interview on Saturday evening.
"I can't say where I'll be going just yet. I'm going to a great, great team, a very special club that is one of the best in the world."
When asked if that meant he was joining Barcelona and might be present when Barcelona face Primera Division Atletico Madrid at Camp Nou next weekend, he replied: "I cannot say anything [about the alleged deal with Barca] but no, I will not [be at the likely title decider in Catalunya]. I will be on holiday."