The Portuguese boss has struggled find his best XI after being hit with a wave of injuries, he has also been forced to rotate players for the Europa League campaign.
However, Neville claims Mourinho needs to build stability, allowing his new players to settle in quicker after their unsettled start to the season.
“It’s going to take some time for United to get through this thing of sacking managers if they don’t come in fourth,” he said.
“They have to really live with Mourinho now and hopefully it will work and he can get it right because we need some stability there.
“I thought United would settle down quicker than they have with the new signings, they haven’t – it looks like it’s still going to be a bit painful.
“Mourinho has always been about picking his best 11 and he will deliver the win. He has had to change it constantly and he doesn’t know his best team yet.”
United have won five of their eleven Premier League matches this season and the pressure has continued to mount on Mourinho and his men.
The Portuguese boss has received two FA charges during his short reign at Old Trafford and following the 3-1 victory over Swansea City, which was their first win in September, the side are sat sixth in the Premier League ahead of their clash with Arsenal at Old Trafford next weekend.