Koeman did not hide his disappointment after the final whistle, criticising both his side's finishing and their overall approach.
"I absolutely hate losing. You have to win this when you get four or five big chances," Koeman told NOS. "If you convert those, a match like this becomes much easier. It shouldn't be a problem then, but in the second half we played worse football. We lacked aggression and it was too nice."
The Dutch coach also singled out Malen's missed opportunities, saying: "He definitely needs to score at least one goal. Normally he does."