Huub Stevens has conceded his PSV Eindhoven side were "simply outplayed" at Ajax on Sunday as the defending Eredivisie champions lost their fourth game on the trot.
The Amsterdammers were too strong for PSV and ran out 4-1 winners with Luis Suarez scoring twice to add to efforts from Miralem Sulejmani and Leonardo.
Ibrahim Affelay scored PSV's sole reply but it was little consolation for Stevens, who was frank in his assessment afterwards.
He told the club's official website: "We were simply outplayed at times. We lost control and we hardy ever won the second ball.
"I maintain that good defending is an art in itself, but not all of my players have mastered that art.
"We did not start well, won too few challenges and gave Ajax far too much space. We did not take the initiative in the first half.
"We wanted to rectify things after the break and showed aggression.
"But I am not pleased at all by the way we conceded the goals."
Meanwhile, PSV have given up on trying to lure Mark van Bommel back to the Philips Stadion in the January transfer window.
Reports in Germany have suggested the former PSV captain will be available as Bayern look to recoup a fee for the 31-year-old, whose contract expires at the end of the season.
But PSV transfers and scouting manager Adrie van Kraaij is adamant the Bundesliga champions have no intention of selling.
"I have read that no-one is allowed to leave Bayern in the winter," he told AD Sportwereld.
"We could offer them one million euros for a player whose contract has just six months left to run but Bayern have no money problems.
"We must get this out of our heads."
Van Bommel, Bayern's first non-German captain, spent six years at PSV before moving to Barcelona for a season in 2005.