Louis van Gaal warned Andreas Pereira he faces plenty of competition to earn a regular place in the Manchester United team after the Brazilian marked his full debut with a goal.
The 19-year-old, who had made two previous substitute appearances, curled in a free kick in United's 3-0 Capital One Cup win over Ipswich Town.
Van Gaal said that Pereira's versatility is a reason why he is at Old Trafford, but told the attacking midfielder he needs to improve because he operates in roles where Wayne Rooney, Memphis Depay, Juan Mata, Ashley Young, Ander Herrera, Marouane Fellaini and Jesse Lingard can also play.
Pereira was chosen on the left wing against Ipswich but can also be used on the right or as a No. 10.
"He can play all these positions and his competitors are Young, Memphis Depay, Fellaini, Mata, Herrera, Rooney [and] Lingard, because he can also play at [No.] 7, 10 and 11," said Van Gaal in a news conference.
"That is the reason I keep these players because then I don't have to keep so many [other] players because I have multifunctional players in Lingard and Pereira. I put always the best player in the lineup when he is working for the team."
Van Gaal said Pereira's free kick came as no surprise to him after watching him work on his set-pieces at United's Carrington training complex.
"He had a big participation on the game because he shoots the free kick in a fantastic way," Van Gaal added. "We know that, he is training that so that is the reason he takes the free kick. But like all the other players there is a lot of space of improvement for Andreas Pereira."
Van Gaal is worried Marcos Rojo's hamstring injury gives him a shortage of left-footed players with Luke Shaw already out with a broken leg. The Dutch boss explained that is why Daley Blind is the only United player to remain on the pitch throughout the season so far.
"Left-footed players are injured, Shaw and Rojo, so I have a problem," he said. "I have changed every player except a left-footed player so Daley Blind has played all the minutes. [Chris] Smalling had also played all the minutes so I bring him out and [Phil] Jones in [as a second-half substitution]. The same with Juan Mata."