WATCH: Diogo Dalot impresses during first appearance in a Manchester United shirt

It's been a difficult week for Manchester United

After losing to Brighton a couple of weeks ago, they followed it with a second defeat on the spin on Monday, at home to Tottenham. Since then, there's been plenty of speculation about the future of Jose Mourinho, with Zinedine Zidane said to be waiting for the green light to replace him as United manager. Ahead of what could reportedly be his final game in charge, Mourinho returned to Old Trafford on Friday night to watch the club's Under 23 side defeat their Stoke City counterparts by a single goal. The United boss spent some of the night sitting with supporters, but will have been keen to watch the performance of Diogo Dalot, making his first appearance in United colours. Dalot was one of only three signings made by the club in the summer, and the Portuguese full-back has been recovering from a knee injury during his first few weeks as a United player. The 19-year-old put in an impressive display on the night, showing glimpses of why the former Porto player is regarded as one of the most highly rated young fiull-backs in European football. Despite a lack of playing time, Dalot appeared defensively sound throughout his appearance. His willingness to bomb forward and join United's attacks will also have pleased his manager and those United supporters in attendance. https://twitter.com/utds_updates/status/1035771045821603840 At this moment in time, Antonio Valencia remains United's first-choice right back. The 33-year-old made his first appearance of the new season in the defeat to Spurs after missing the Leicester and Brighton games through injury. Given his age, it's likely that Dalot will deputise for the Ecuadorian as the season progresses. Matteo Darmian, who filled in for Valencia during his injury, was expected to return to Italy this summer. Although that didn't happen, it's thought a move could still happen for him in January, meaning Dalot will be one of only two right backs available to Mourinho.