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Bellingham arrived from Sunderland in a €33 million ($59 million) deal ahead of the FIFA Club World Cup and started three of Dortmund's five games in the tournament, hosted by the United States.

However, the midfielder has only started two of Dortmund's four Bundesliga matches so far this campaign, with Kovac's team starting strongly with 10 points.

Bellingham has only played 153 minutes in the German top flight and he was limited to substitute appearances in Dortmund's past two matches – wins over Heidenheim and Wolfsburg.

However, Kovac still believes Bellingham will adapt to his surroundings quicker than most young players.

"Everyone wants to play more," Kovac said. "Everyone wants to play all the time. But then you can only start 11 players. 

"When you sign a contract here, it's not only well-paid, but it also means there's a hell of a lot of competition.

"Jobe is a very talented player, but he obviously comes from the English second division. He has great potential, but he naturally has to grow into the game here.

"We can't expect a player to have everything I want down perfectly within two months. It's a process.

"Young players sometimes need up to six months, but I'm convinced it'll happen faster. It will all come together, we're sure of that."

On Sunday (AEST), Dortmund visits a Mainz team that has four points from its first four games, trouncing Augsburg 4-1 for its first victory of the campaign last week despite a red card for defender Dominik Kohr.

Kovac expects Bo Henriksen's team to pose a difficult challenge for his side, too.

"They have developed very well under him, even if they didn't start this season as they would have liked," Kovac said.

"They are a very difficult opponent. They have strong running and high pressing. We won the last game against them [3-1 in March] but we didn't blow them away."