Japan forward Shinji Okazaki made his debut for Mainz in a 2-1 away win to Fortuna Cologne in the German League Cup on Saturday.

Okazaki started on the left side of midfield before sliding up front for the second half for manager Christian Heidel, whose side launches its Bundesliga campaign on Aug. 11 at home to Stuttgart — Okazaki's former club.

"There's plenty of room for improvement," said Okazaki, who came off after 80 minutes without a goal against Fortuna of the Regionalliga, the de facto German fourth division. "We couldn't execute the game plan.

"It would be nice to score (against Stuttgart)."