Despite their opponents playing the last half an hour with 10 men, Lionel Messi and co. were unable to secure all three points at Mendizorroza.
"I wasn't happy with the first half," said Koeman.
"I made three changes because I wasn't happy and there were some players on a yellow card.
"If you criticised me the other day for making changes too late, today I made changes at half time. I wasn't happy with our first half and there were people on the bench with the capability of scoring. I wanted to change things to win the game."
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