Chelsea are yet to see the best of the Germany internationals since spending £142million on the Bundesliga pair in the summer, and countryman Gundogan believes that their gradual adaptation to the Premier League is "normal".
Discussing Chelsea ahead of City's trip to Stamford Bridge on Sunday, Gundogan told Sky Sports: "They have two new German players who have tried to adapt as well as possible.
"In general, I think it's not easy to adapt quickly to the Premier League when you come from a different country and now, with the situation going on, I think it's just even harder.
"So I think it's quite normal that they are struggling a little bit, but they both have incredible talent and I'm sure they will both be able to prove it in this league."
Gundogan feels that Blues boss Frank Lampard invested his ample financial resources wisely in the close season and has built a squad that will challenge for the title.
He said: "Like every year, Chelsea have a great squad with incredible players.
"They got some really talented young recruits in the summer, spent a lot of money and got some really good players so I think they will do well.
"They are also a team that struggles like everyone does but they have a lot of quality and it's going to be a great game on Sunday."
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