With Paul Pogba and Alexis Sanchez particularly profligate, United was terrible in the first half and conceded the opening goal when Andros Townsend's shot from the edge of the area spun into the top corner off the back of United defender Victor Lindelof in the 11th.
Mourinho started by saying that "Marcus was good" when he came on for Scott McTominay at half-time as he "immediately created unsafe situations and opened more spaces" for other players to get into and that caused chaos for the Palace defenders.
Nemanja Matic doesn't score many goals, but when he does, they're usually absolute screamers.
But Mourinho will take heart from the way his players shrugged off their limp opening to move back above Liverpool into second place in the Premier League and within 16 points of runaway leaders Manchester City.
"We started bad once more".
They are not in Champions League action until next week, and go into the game on a high after coming back from 2-0 down to win 3-2.
The three vital points took United back up to second in the Premier League.
"The message was: half I can not tell you because you would have lots of (bleeps) on the television, half of it was tactical information".
"But you can see how close we are as a group that everyone celebrated together, and how much it means to us, because that was a huge win".
Fortunately for Pogba, he sparked into life following Smalling's goal and even had a curling shot pushed away by Palace goalkeeper Wayne Hennessey.
Palace, which is in the relegation zone, also conceded an injury-time goal to lose to Tottenham 1-0 in its previous game.
"His great weakness is that he plays like he's playing in the park with his mates", said Neville during the half-time analysis on Sky Sports.
"What I can say was all about the tactical positioning".
"The only thing that has disappointed me today is the fact once again we go away with no points".
United players might think twice next time they try to tell Matic not to shoot with seconds remaining of a game.