The 18-year-old was signed by the Red Devils on transfer deadline day for €25m which could rise to €40m after scoring eight goals and making 11 assists last season.
It was agreed that the forward would arrive at Old Trafford in January, subject to securing a work permit, so that he could continue developing with Atalanta.
And footage has emerged from his first ever Champions League appearance shows he is getting comfortable playing at the top level.
In the clip, Diallo has been on the pitch for nine minutes as his side are 1-0 down at home to Midtjylland.
Running into the penalty box on the left wing after 77 minutes, he receives the ball from Matteo Pessina.
He flicks the ball with the heel of his left foot which gives the forward time to turn and face goal.
Coming under pressure from Joel Andersson, Diallo performs a cheeky stopover that pushes it out to the right.
Striding towards the ball, the Ivorian lines up a curling shot with his weaker right foot.
And it curls towards the far post, needing a diving save from Marco Sportiello to stop Atalanta grabbing an equaliser that they eventually get through Christian Romero’s header two minutes later.
This footage was soon shared on social media, where the United faithful were left in awe at their new young talent’s skills on his right foot.
“This boys electric – I like what I saw,” one supporter said.
Another commented: “If this is him on the wrong side, imagine him on the right one.”
While a third compared him to a footballing superstar United will see soon, with: “[Kylian] Mbappe-esque.”
And a fourth added: “Obviously prefers his left foot but equally comfortable on the right. Exciting prospect.”
It is not the first time Diallo has impressed United fans as his skills in Atalanta training emerged last month.
Performing some incredible skills with the senior squad, the 18-year-old has earned some big predictions from insiders at Old Trafford.