Ole Gunnar Solskjaer says Manchester United has to prove it can be consistent if it is to compete with Liverpool and Manchester City for the Premier League title next season.
Ahead of a derby clash with rival City at Old Trafford on Wednesday, United is 24 points behind leader Liverpool, although it has played one match fewer.
Solskjaer's side faces a battle for Champions League qualification with United, which has lost six of its past eight games in all competitions, three points behind Chelsea in the race for a top-four finish.
United has not won the Premier League since Alex Ferguson retired in 2013 and Solskjaer is uncertain over how competitive the Red Devils can be in 2019-20.
"I don't think we've got the consistency to do that," Solskjaer told reporters, when asked if United can fight City and Liverpool for the title next season.
"Over the last 18 games, we're not far away from them but it's doing it over the course of a season. We've done it for half a season now. Let's see. You can never say never.
"You cannot expect things to happen overnight and we know that. It will happen gradually and we have to be realistic enough as a club that we have to take it step by step.
"That's not changing 10 players now and bringing 10 players in. It's slowly, slowly but surely. It has to be the right quality, right personality, the right standards to get us back to where we want to be."
United fans have been left to weigh up whether they would rather see neighbour City or equally fierce rival Liverpool be crowned champion.
"It's not about taking something away from others," Solskjaer added. "We have to want to overtake them, and not just because it's City and Liverpool.
"For a supporter, as I am, and as a manager now as well, we know [them well] because they are so close in the vicinity.
"We want to be the best, we have been the best and it's not nice seeing those two at the top."
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