Wolverhampton Wanderers manager Walter Zenga has said that his side need to develop "a killer instinct" after they edged past League Two outfit Cambridge United in the second round of the EFL Cup.

Goals from Helder Costa and Jed Wallace put the home side two to the good inside 13 minutes, but just one minute later Medy Elito struck back for the U's - currently bottom of the Football League - to keep the tie alive.

That was to be the end of the goalmouth action at Molineux, however, as Wolves spurned several second-half chances - including a missed penalty for the second successive home game - on their way to a place in the third round next month.

"We must be more determined. Then you can open the game and you never know what happens," Zenga told the Wolves website after the game. "When you create situation like we create, and we miss one versus one and the penalty again, we must understand we must close the game and be more strong, determined and have a killer instinct.

"The important thing is to win. Then sometimes it's the attitude of the team that is different. Either it's difficult to play at this level and keep the same concentration at a high level for a long time.

"In the end we won, we created more chances in the second half, but it's okay."

Wolves remain unbeaten under Zenga this season and currently sit third in the primitive Championship table.