Erik ten Hag said there was room for improvement despite a 4-0 rout of Sonnenhof Grossaspach in his competitive game in charge of Bayer Leverkusen in the DFB-Pokal. 

Ten Hag watched on as last year's Bundesliga runners-up ran riot at WIRmachenDRUCK Arena, with Patrik Schick's opener in the 32nd minute giving them a half-time lead. 

Leverkusen's task was made a little simpler in the 66th minute when Grossaspach captain Volkan Celiktas received his second yellow card just two minutes after his first. 

They made their man advantage count eight minutes later through Arthur, with the hosts then reduced to nine men after Mert Tasdelen was handed a straight red card. 

And two goals in three minutes late on, courtesy of Christian Kofane and Alex Grimaldo, the latter from the penalty spot, added further gloss to the scoreline.

Indeed, Leverkusen registered a mammoth expected goals (xG) total of 4.37 from their 20 shots, compared to Grossaspach's 0.62 from their 12 attempts at Mark Flekken's goal. 

"Grossaspach played well and caused us problems," Ten Hag said. "In the end, we deserved to win. 

"We had some good spells but there is still room for improvement. We will continue to work on that."

Ten Hag, who took over from Real Madrid-bound Xabi Alonso in May, has overseen a period of transition at Leverkusen after several key players left the club. 

Florian Wirtz, Jeremie Frimpong and Granit Xhaka have all departed for pastures new, while Flekken, Kofane, Axel Tape, Ernest Poku, Ibrahim Maza and Jarell Quansah all made their competitive Leverkusen debuts on Friday. 

"Of course, it needs time. You can see not every action worked out," Leverkusen sporting director Simon Rolfes said of the changes.

"But we saw today that we've got interesting young players. Ibrahim Maza did well and showed his qualities between the lines.

"And that's why it will take a little time, but we still have a good team."

Leverkusen start their Bundesliga campaign next Saturday with a home clash against Hoffenheim.