Adnan Januzaj sent a message to Manchester United manager Louis van Gaal with a hat-trick against Sunderland in the Under-21 Premier League on Monday.

Januzaj struck twice in the first half either side of Andreas Pereira's goal before completing his treble after the break to cap a 4-0 rout of the Black Cats at Old Trafford.

Luke Shaw played his first 45 minutes in a United shirt following a month out with a hamstring injury, setting up Pereira's goal before being replaced by Ben Pearson at the break.

Shaw was an unused substitute in the Premier League win over Queens Park Rangers on Sunday and is now in contention to make his competitive debut against Leicester City this weekend, as is Januzaj whose own fitness is improving following the World Cup.

The Belgian youngster has featured in each of United's four league games this season, though only from the bench after attending just a week of pre-season training before the start of the campaign.

However, the 19-year-old looked close to his very best in disposing of Sunderland and took just 19 minutes to open his account for a United team also boasting Anderson and Will Keane, as he steered home from inside the box.

After Pereira had powered in a second from the edge of the area after Shaw's low cross, United were nearly out of sight when Keane cleverly released Januzaj who finished past Sunderland keeper Maksymilian Stryjek.

And Januzaj completed his hat-trick after Marnick Vermijl's pull back, sliding into an empty net to cap an evening which will leave Van Gaal with plenty of food for thought ahead of the remainder of the season.

Having enjoyed his breakthrough campaign last season under David Moyes, Januzaj has seen Juan Mata and Angel Di Maria arrive in the last two transfer windows while Van Gaal's recent switch to a midfield diamond could also restrict his opportunities.

The return to full fitness of Shaw, who was heavily criticised by Van Gaal during pre-season, is a welcome boost to the former Netherlands coach who despite signing Marcos Rojo is low on defensive resources.