Leroy Sane will "unfortunately" give Bayern Munich a lot of joy, according to his former Schalke team-mate Joel Matip.
Bayern last month completed their lengthy pursuit of Sane, agreeing a €60million deal to sign him from Manchester City as he entered the last year of his contract at the Etihad Stadium.
The transfer was announced between the Bavarian giants clinching an eighth successive Bundesliga title and completing a domestic double by winning the DFB-Pokal.
Liverpool defender Matip believes Sane is bound to have a big impact at Bayern, though he worries the addition could stifle competitiveness in Germany's top flight.
"I know him well. He is a top player. Leroy will unfortunately give Bayern a lot of joy," Matip told Die Welt.
"Well, [it's unfortunate] for the competition, which already has a hard time. It won't be easier to keep up with Bayern.
"Leroy is a player who can help the team enormously."
An anterior cruciate ligament injury limited Sane's involvement for City this season, which saw Liverpool claim their first league title since 1990.
Asked if winning the Premier League was bigger for the Reds than last year's Champions League triumph, Matip said: "It was like that, but that has to do with the club, which had to wait 30 years for it.
"In addition, each club ticks differently. At Manchester City, the Champions League may be worth a little more."
Jurgen Klopp's Borussia Dortmund in 2012 were the last team to deny Bayern the Bundesliga title and Matip praised the manager's achievements since moving to Anfield, where he has also won the UEFA Super Cup and Club World Cup.
"He is known for being casual, but when it comes to work and the team, he is very clear. He has his ideas and always tries to get them into the mind of every player," said Matip. "He has an incredibly good way of motivating us and stirring the emotions within us."