Japan international Yoshinori Muto made his debut in Mainz's 3-0 win over third-tier Cottbus in the German Cup on Sunday but lamented his performance off the bench.

Muto had a 20-minute cameo in the second half with his team up by three, playing as the single striker. He had an excellent opportunity shortly before the final whistle to give Mainz a four-goal lead but blasted over the bar for a miss the former FC Tokyo man hugely regretted.

"You have to take your chances when you get them," Muto said. "I'm not happy about it. There were a few situations where I thought I would've had a chance had I gotten the ball. I need to be more vocal and start demanding the ball."

Mainz will open its Bundesliga campaign on Saturday at home to Ingolstadt 04 and Muto is fully aware he will have to step up his game in order to get the new phase of his career off to a solid start.

"The teams we face in the league are going to be stronger and things will get even more difficult," he said. "If I don't learn to communicate, I won't score."