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Despite playing four years above his age, Gabriel scored two goals on his debut for the Red Devils' U18s in April. He contributed a brace in a dominant 13-1 victory over Leeds United.
Gabriel's talent has even seen him secure a lucrative sponsorship deal with Nike. He was being tracked by various top clubs across the continent, but United director of football Jason Wilcox and director of football negotiations Matt Hargreaves personally stepped in to convince the teenage prospect his future was at Old Trafford.
They handed him an official squad number, the No. 95, which is understood to be the highest number any player in United history has ever worn. Speaking about the teenager, specialist one-to-one football coach Alfie Brooks, who has worked with the United star, offered an insight into how good Gabriel is.
Brooks said: "When he first started training, [his competitiveness] was the standout attribute. I've coached nearly 1,000 academy players over my time.
"Four of them in Josh Nichols (Arsenal), Josh Acheampong (Chelsea), Sydie Peck (Sheffield United) and Tyrique George (Chelsea) have made their senior debuts - and JJ is the best I've ever seen. He could go into a Premier League changing room right now and technically he would be better than all of them. It wouldn't even be close."
Despite impressing for the U18s, he will not be allowed to compete in the Red Devils' bid to win the FA Youth Cup, because he is not old enough. While he is permitted to play in the Premier League U18 division, players competing in the Youth Cup have to be born before 31st August 2010.
Meanwhile, Dowman made many appearances in the Gunners' summer pre-season tour of Singapore and Hong Kong, winning penalties against Newcastle United and Villarreal.