MANCHESTER, England, Jan 31 (Reuters) - Manchester United ( MANU ) manager Ruben Amorim has praised Argentine winger Alejandro Garnacho's changed attitude since being dropped last month and said the club want to continue improving with the youngster.

Garnacho came on as a second-half substitute in United's 2-0 Europa League victory over Steaua Bucharest on Thursday and the lively 20-year-old set up Kobbie Mainoo for his side's second goal.

"He changed right away since that game from City," Amorim said of the player's response to being left at home for December's away clash at Manchester City along with fellow-forward Marcus Rashford, who remains out of favour.

"The way he understands things and understands that I just want to help him, I just want to win games. He changed in everything, the approach when I talk with him, the way he recovers.

"He understands that sometimes I am a different coach, that I am demanding in my way.

"I think all the merit is from Garnacho and he is improving, and we want to continue to improve with Garnacho," added the manager, whose side are at home to Crystal Palace in the Premier League on Sunday.

Media reports have suggested Garnacho could leave United, with Napoli and Chelsea reportedly interested, but Amorim's comments suggested the player has a clear future at Old Trafford.

The Portuguese boss also said Mainoo was playing with a smile on his face again after recent uncertainty over his future.

"The key point is the position. It's different for him, it demands a lot from him," he explained of Mainoo's more forward role as an attacking midfielder.

"In that position I feel him happier to play... simple as that. I don't look about just the movements, the way he touches the ball, I feel it just watching him -- he was so happy on the pitch.

"That is important for me because if they are happy, they play better. So, I think he can change position."

Amorim provided an update on injured England defender Luke Shaw, who suffered a setback last month less than two weeks after returning to action from a long layoff but is now back in training.

"It will take a little bit more time. I think he needs to train more, to spend more time with the teammates playing normal or small-side games, not just working alone," said the manager.

"When I feel it is the right moment, we will start with some minutes in the games."