The Red Devils confirmed on Thursday that their Ivorian winger had resumed first-team training at Carrington as he looks to build up match fitness ahead of a return to action.
Diallo, who has nine senior United appearances to his name to date, has yet to play at all this season after suffering a serious knee injury during United's pre-season friendly win over Arsenal in the United States in July.
It was a frustrating setback for the 21-year-old, who is highly-rated at Old Trafford and shone during a season-long loan spell in the Championship last term as he scored 14 goals in 43 appearances for Sunderland en route to the play-offs.
The four-cap Ivory Coast international, who joined United from Serie A side Atalanta in a £37million deal in January 2021 and also spent time out on loan at Rangers, would have hoped to make a significant impact at United this season under Erik ten Hag or at least continue to prove his worth with another productive loan move.
Now Diallo is inching closer towards a long-awaited return, having officially returned to training this week.
He is likely to remain a little while away from a return to senior action as he carefully builds fitness and it will be interesting to see if he forms part of the United squad for the second half of the season or if another loan deal is sought in the January transfer window.
The wide areas have been notably problematic for the under-pressure Ten Hag during a frustrating campaign to date, with the likes of Antony and Marcus Rashford struggling for form, Jadon Sancho banished from the first-team picture and Alejandro Garnacho remaining a largely inconsistent proposition.
Diallo will no doubt be buoyed by the recent first-team breakthrough from fellow youngster Kobbie Mainoo, who has impressed after being handed his chance in midfield.
He may also be eyeing a late push to try and make the Ivory Coast squad for next month's Africa Cup of Nations, which is taking place on home soil.
While Diallo is closing in on a comeback, there are still several players in the treatment room at United, who, after brushing aside Chelsea in midweek, will look to make it back-to-back wins to continue to ease the pressure on Ten Hag when they host Bournemouth at Old Trafford in the Premier League on Saturday.
Casemiro, Lisandro Martinez, Christian Eriksen and Tyrell Malacia are all still out along with Sancho, while Raphael Varane missed the 2-1 win over Chelsea on Wednesday with a back issue.