Ronald Koeman was frustrated with Everton's failure to build on a positive first half in their Europa League clash with Hajduk Split, despite a comfortable 2-0 win in the first leg of their play-off tie.
Everton enjoyed a fine opening 45 minutes and led through goals from Michael Keane and Idrissa Gueye, but they could not add to their lead after the restart and were reliant on goalkeeper Jordan Pickford for a pair of important late saves.
Koeman quickly identified the differing performance levels as an issue, speaking of his disappointment after a stalled second-half display.
"I was really happy with the first half and unhappy about the second," the manager said. "We lost a big opportunity to score more goals and secure qualification.
"Hajduk had two or three chances to make it 2-1 - we were lucky."
Defender Keane netted his first goal for Everton, while fellow recent recruit Pickford excelled, and Koeman has been pleased with a back line that is yet to concede in four games this term.
"I'm really happy it's the fourth clean sheet in a row," he said. "That's a positive and it starts with good defensive organisation and a good goalkeeper.
"There was one goalkeeper on the pitch who played at a high level for 90 minutes and that was Jordan."