That is according to Red Devils great Jaap Stam.
United host Arsenal on Sunday (4pm) 16 points adrift of champions Chelsea.
The Gunners are two points clear of Louis van Gaal's men and a victory will all but ensure a top-three finish for them as they have a game in hand over their rivals.
They need to defend a bit better. Chelsea not playing most attacking of football but they get results
Jaap Stam
But Stam, who made 125 appearances for the Red Devils during a three-year spell at Old Trafford, believes both sides need to be more organised defensively if they are to topple Chelsea next season.
"Maybe they need to defend a bit better. Chelsea not playing most attacking of football but they get results. You need that as a team," Stam told the club's official website.
"Every manager has their open way of playing. Mourinho's chosen this style and they get results.
"Good for the team and the players. If they defend a bit better, you will get results and win the league as well."