It will "take a long time" for Manchester United to challenge for the Premier League title again, says manager Ole Gunnar Solskjaer.
United ended their season with a dismal 2-0 home defeat against relegated Cardiff to finish sixth, 32 points behind champions Manchester City.
The Red Devils won just one of their last seven league games.
"The last couple of months have been extremely hard for the team, the club and for the players," said Solskjaer.
United finished second under Jose Mourinho last season, but the Portuguese was sacked in December following a run of poor results.
United ended their season with a dismal 2-0 home defeat against relegated Cardiff to finish sixth, 32 points behind champions Manchester City.
The Red Devils won just one of their last seven league games.
"The last couple of months have been extremely hard for the team, the club and for the players," said Solskjaer.
United finished second under Jose Mourinho last season, but the Portuguese was sacked in December following a run of poor results.