He still makes mistakes, and hasn't suddenly become Roy Keane, but his presence in the side is now a goal threat for his side, not the opposition.
Marcus Rashford showed clever footwork to deceive Palace full-back Joel Ward down the left, then pulled the ball back for the unmarked Mata to sweep in from 12 yards.
Bournemouth and Leicester's troubled starts to the season continued as both sides played out a goalless draw at the Vitality Stadium.
"Mkhitarayan played and Fellaini didn't in Russian Federation. We have to go away with the national teams and come back fit".
Manchester United had the flawless start to the match as Marcus Rashford turned past Joel Ward cleverly before driving into the box and picking out Mata who calmly slotted the ball into the bottom corner to open the scoring just three minutes in.
He has gone from a joke figure at Old Trafford to a key player in this Mourinho team. United, who have scored 17 league goals, will be favoured for a huge win at their home.
With Manchester City facing champions Chelsea at Stamford Bridge later on Saturday, United temporarily moved to the top of the Premier League as Lukaku scored his seventh goal in his last six appearances.
The Red Devils are coming off a strong 4-0 win at Everton in their last league contest at The Theatre of Dreams.
The sequence occurred just three minutes into the Premier League matchup and led to United's first goal early in the game. The Eagles are now dangerously close to Halifax Town's all-time record of failing to score in their opening eight league games of the 1990-91 campaign.
"With Christian Benteke injured, it does not look good for the Eagles at the other end either, and their wait for a league goal might have to go on until after the worldwide break".
Indeed, the Portuguese manager will be without as many as seven first-team players ahead of the visit of Roy Hodgson's men on Saturday.
"Three points and a good performance".