A week after an inspiring comeback win against ManchesterCity, Manchester United fell to a 1-0 defeat at Old Trafford against bottom club West Bromwich Albion on Sunday and manager Jose Mourinho said such inconsistency needed to change if they were to challenge their neighbours next season.
The loss handed City the title, leaving United trailing by 16 points with five games remaining, and Mourinho immediately faced the question of whether he was confident his team could make a real challenge next year.
"I trust in my work, that is for sure, I have no reason not to trust. Eight titles are eight titles and three Premier Leagues are three Premier Leagues," he said.
"The last title was not 20 years ago it was three years ago. I know how to win, I believe in myself but I don't play," added the former Chelsea and Real Madrid manager.
"In my experience you don't win titles with inconsistency, you win titles, of course with quality, without quality you have no chance, but you have to win titles with consistency at every level not just the performance level.
"The mental level, the day by day, everything must be consistent until the last day so one of the things we have to improve is consistency," he said.
Mourinho suggested his players might have over-reacted to the win against City at the Etihad.
"Probably because I won eight championships I was not on the moon with the victory against them because that doesn't make me feel super-happy. In my opinion it affected for sure some of the people that were too happy just with that," he said.
A 73rd-minute header from Jay Rodriguez after United had failed to defend a corner won the game for relegation-threatened West Brom and Mourinho said his team had not played the simple football he expects.
"We were masters in complication. Everything was complicated. We couldn't think fast, we couldn't play fast. Players didn't want to or didn't play simple. Everything was slow. Everyone was one more touch, one more trick, one more flick, one more turn.
"We always gave them the opportunity to be solid, compact, together with huge physical strong players, they always had time to organise themselves. When we had the ball, we wanted to run, dribble and everything was complicated," he said.
The Portuguese manager said that City deserved their title and he had offered them his congratulations after the derby win.
"I don't know if I was the first or second or third but I congratulated them face to face when I had chance to do it. I knew that sooner or later that would be and if I was in that position I would be very upset if someone said they won the title because Manchester United lost," he said.
"They won the title because they were the best team. They lost only two matches, that is why they were champions."