"It is deteriorating further," said Cocu after PSV saw a half-time lead overturned at struggling Willem II Tilburg on Saturday and had to scurry for a 2-2 draw.
"After we went 1-0 ahead we had to make more things happen. It is really important that we now go and look at this problem."
It was the fifth time this season that PSV have taken the lead in a league match but ended up either losing or drawing. "It has happened too many times," said Cocu.
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"In matches against top opposition we rise above our potential. But these kind of games are just as important. We also have to bring our motivation to these games. It is sour to lose and if we want to win any prizes this season we are going to need to change it."
PSV meet Manchester United, coached by Dutchman Louis Van Gaal, in the Champions League at Old Trafford on Wednesday.
(Reporting by Mark Gleeson; Editing by Alan Baldwin)
