Cocu blamed a lack of focus for the 1-1 home draw with struggling Heerenveen on Saturday, which has opened the door for title rivals Ajax Amsterdam, the only other team with realistic title aspirations, to take over the league's leadership.
"I asked my players at half-time whether they were playing below-par because their minds were elsewhere. The players knew they could have been a lot sharper. The second half was better but still not good enough to win," Cocu told reporters.
PSV meet Atletico Madrid in the second leg of their Champions League last 16 tie on Tuesday after a goalless draw in the first leg last month.
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But Cocu said there would need to be a considerable improvement on Saturday’s performance if they were to have any chance of progressing.
"We played well beneath our level. That is not acceptable. We had to keep working as hard as we could, putting in some heavy effort and proving convincing. But that I did not see any of this in the first half.
"We fought against ourselves. We lost too much possession and made too many mistakes. Even when we equalised to make it 1-1, I thought I would see more but our final passes were too sloppy."
After playing Atletico, PSV then take on Ajax in a potential title decider next weekend.
"We’ve lost important points but that changes nothing as far as next week’s duel is concerned. We are going to play to win but it is going to have to be a lot better than it was today,” the PSV coach added.
(Reporting By Mark Gleeson in Cape Town; editing by Amlan Chakraborty)
