Tottenham manager Jose Mourinho says he was "destroyed a little bit on the inside" by his team's 3-1 defeat at Sheffield United on Thursday.
Spurs were runners-up in last year's Champions League under Mauricio Pochettino but are currently ninth in the Premier League table, nine points behind fourth-placed Chelsea.
Asked about Thursday's loss, Mourinho said: "I thought that by a desire point of view, they put more than us.
"That's something that disturbs me.
" Spurs have qualified for the Champions League for the last four seasons and have not finished lower than sixth in 11 years, but Mourinho's side have won just one of their last six Premier League matches.
The defeat at Bramall Lane, in which a Harry Kane equaliser was controversially ruled out by VAR because the ball had brushed the tumbling Lucas Moura's hand in the build-up, saw Sheffield United move above Tottenham in the table.
Mourinho, who succeeded Pochettino in November, said: "There was a lot in the game, there was a possibility of shortening distances to Champions League positions, there was the possibility of being more stable for the Europa League positions fight.
"It's something that destroys me a little bit on the inside because I think the last thing in football is when you have the feeling you could, you should do more.
" The Portuguese insists there is one factor required in his attempt to revive fortunes at Tottenham.
Only time," he said.
"One of the most difficult things in football is exactly that, to change mentalities.
It's to change state of mind.
It's to change the team's soul.
It's one of the most difficult things in football.
"Sometimes you have incredible luck to have a majority of players adapted to these needs and some other times you have incredible players but the psychological profile is different or was built in a different direction.
So only time can do it.
" Tottenham's next game is at home against Everton on Monday.