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'm worried by our performance in attack," Koeman said afterwards. "It's not an attitude problem, nor concentration, but it's a question of being more assured in front of goal.
"It happened to us against Juventus and today as well. Furthermore, we gifted Alaves their goal. But if we create that many chances, we can't miss so many. If you create chances and you only score one, it's not good.
"Of course I'm worried that we've only picked up two points from the last 12 [available]. I think the play has been, in general, very satisfactory. I'd be more worried if we weren't creating chances.
"We have to perform better in front of goal. The final pass, the final shot. We can't miss so many [chances]. We're missing too many."
Koeman explained his decision to make three substitutions at half time at Mendizorroza.
"I wasn't happy with the first half," he continued. "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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