Frank De Boer slammed his forgetful Inter Milan players after a shock 2-1 San Siro defeat to Cagliari left the Nerazzurri 10 points behind Serie A leaders Juventus on Sunday.
Inter started the season with new Chinese owners and fresh ambitions after capturing a number of top players in the close season.
But eight games in, their enthusiasm has been replaced by despair as an ongoing row between club captain Mauro Icardi and irate 'ultra' fans of the club has added to shaky results on the pitch.
"No disrespect to Cagliari, but against them Inter should be winning," De Boer fumed in comments to Premium Sport after Inter's third defeat in eight games.
"After we scored our goal, we forgot to play."
A week ahead of a tough trip to Atalanta, who stunned Napoli 1-0 in Bergamo a fortnight ago, Inter are in crisis.
Inter management warned even before kick-off they could concede to demands by fans to strip captain Mauro Icardi of the armband over allegedly exaggerated comments he made about them in a recently-published autobiography.
On Sunday morning, fans issued a statement aimed at Icardi, declaring: "For us, you are finished. TAKE THE ARMBAND OFF, YOU CLOWN."
Icardi earned a chance for appeasement when Inter were awarded a penalty in the 25th minute after he was manhandled by Bruno Alves in the area.
But he fired his low drive wide of Marco Storari's upright, spurning the chance to pull level with Serie A goals leader Edin Dzko, who took his tally to seven with a brace for Roma in a 3-1 win at Napoli on Saturday.
It was the third time Icardi had failed from the spot in his last four attempts in the league, and although his miss would be felt by full-time it was actually applauded by some sections of the stadium.
Portugal midfielder Joao Mario eventually broke the deadlock when he beat Storari at the second attempt on 56 minutes.
But Cagliari drew level when Federico Melchiorri sprung the offside trap to flick past Handanovic on 71 minutes.
Melchiorri almost had his second with a diving header that went inches wide, but the big striker made amends with a cross that took a deflection off Jeison Murillo before Handanovic bundled it over the line five minutes from the end.
De Boer said he would reserve judgement on Icardi "until Monday", when the player is expected to meet management for clear-the-air talks.
But vice-president Javier Zanetti said earlier Sunday Icardi risked being stripped of the captaincy, and sporting director Piero Ausilio, speaking after the game, said he was "livid" at the turn of events.
"Personally, I don't think that at 23 years old you should be writing a biography," Ausilio told Sky Sport.
Asked if it was his "toughest" spell since joining the club from Ajax, De Boer said: "Yes, that's right. I didn't expect this defeat. We were in command of the game and then we stopped.
"In the second half we struggled to control the midfield and we lacked competitive spirit and for me, that's no good."
Cagliari earned promotion to Italy's top flight at the end of last season, and celebrated their second successive win over Inter at the San Siro having triumphed in 2014 when current Hamburg midfielder Albin Ekdal hit a hat-trick in a 4-1 upset.