Kai Rooney reached an early career milestone by making his debut for Manchester United Under-21s on Friday.The son of Man United and England legend Wayne Rooney, Kai came off the bench in a Premier League 2 clash against Nottingham Forest.Kai Rooney signed first-year scholarship terms with Man United in JulyHe’s still only 16, the same age as his dad when he made his first-team debut for Everton.What happened on Kai Rooney’s Man United Under-21 debut?Unfortunately, his Under-21 debut didn’t go to plan as United conceded a late goal to lose 3-2 in the game being played at Loughborough University.Nonetheless, Rooney Jr’s appearance represents the next step in his burgeoning career as he looks to follow in his dad’s footsteps.Rooney was among United’s new academy intake this summer, signing as a first-year scholar.Also in that crop was Jacey Carrick, the son of current United head coach Michael Carrick.Born in Liverpool, Rooney first joined the United youth set-up back in 2016.After also spending time with Manchester City and then in the USA after his dad moved to D.C. United, he re-joined the Red Devils in 2020.And ultimately, his goal is quite clear: to reach the first team.What has Wayne Rooney said about Kai?Speaking about his son last month, Wayne Rooney told talkSPORT: “Kai has signed a long-term deal at Man United and he’s at the place he wants to be, the place I want him to be.“That’s important. He’s been at the club a long time and he wants to go and try and play for the first team and be successful.”Wayne Rooney says Man United is the right place for Kai to be and will hope to see him follow in his footsteps by breaking into the first teamGettyBut for the time being, he’ll hope to continue his development with the Under-21s, who are managed by Adam Lawrence.United are back in Premier League 2 action away to Burnley in early November.Meanwhile, the first team’s woes worsened in midweek with a 2-0 Champions League defeat to Atletico Madrid.After that game, United defender Lisandro Martinez sparked controversy by openly criticising the club’s board.He has since apologised.United’s search for a first win in six outings takes them to old rivals Leeds on Sunday.