Antonio Conte believes Tottenham have collectively forgotten how to "suffer" and grind out results after their capitulation against Manchester City.
Spurs blew a two-goal lead at the interval to slide to defeat against the Premier League champions on Thursday, going down to a 4-2 loss at the Etihad Stadium.
The result keeps the north London outfit well adrift of the top four, with a five-point gap between them and fourth-placed Newcastle United, with the Magpies also possessing a game in hand.
For Conte, whose long-term future at Tottenham remains a cloudy prospect, the manager thinks his side have lost their readiness to battle through the difficult moments this season, and he challenged them to show a "nasty" streak.
The Spurs spirit will next be put to the test at Fulham on Monday evening, with the Cottagers just two points adrift of Tottenham.
"I think that maybe we have to improve the spirit, the collaboration, the will and the desire to suffer," Conte said. "Maybe we have forgotten to suffer and to understand that.
"If we want to win the game, sometimes you have to stay there to suffer and defend the result, [with] the will and desire to not concede a goal."
Defeat to City marked a third loss in five Premier League games since Tottenham returned to domestic action following the mid-season World Cup break.
A draw with Brentford and a victory over Crystal Palace have been their other results, along with an unconvincing FA Cup win over third-tier Portsmouth.
Conte remains insistent he is seeing improvement from his side up to a point, saying: "I think that we are making progress in my opinion, in my mind, in some aspects.
"[But] in other aspects, I think that we have to come back like last season and be a bit more solid, a bit more focused, a bit more nasty.
"I think that we have to try to find the same solidity as last season and to learn again to suffer at the moment that we have to suffer. I think that we are [headed] in the right direction from my experience."