Gabriel, 15, formally asked Man United to cancel his registration in September, effectively seeking to leave the club as several top European clubs circled.
The Red Devils have rejected the teenager's formal request for his youth registration at the club to be terminated.
However, JJ Gabriel has an Irish passport through his father, meaning that a departure to a European club when he turns 16 in early October could happen.
Gabriel must plus play first team football
Barcelona, Real Madrid, Paris Saint-Germain and Manchester City have all been reportedly interested in the teenager as he ponders his future away from the Red Devils.
Speaking to Chase football coaching programme, Heskey opened up on the situation where he believes Gabriel needs to leave and play first team football immediately.
“I think, yeah, at 15, you just want him to enjoy himself and go and play. Because you never know what's going to happen down the line.
“He's soon to be 16. You've got potentially a massive career ahead of you. You don't want to do something silly. Look, he's got his people that are taking care of him. I believe that they know the best route for him.
“His route is, can I play first-team football? And where is the best place for me to play first-team football consistently and get the best out of myself in the system that they play? Whether it be at Man United, whether it be wherever, I think they said Barcelona, Real or whoever it may be, it's how you get into that first team.
“If you believe that at 16 your role is to go to Real Madrid and you'll get first-team football, well, we'll take our hat off to you. But you've still got to go and do it. Because no-one's going to be looking back at you and saying, ‘19, 20, and you've made five appearances, yeah, it's the right move’. No, you've got to be playing first-team football.”
JJ Gabriel has scored 29 goals and registered four assists in 32 appearances for Man United Under-18s, while he scored a hat-trick against Sabah Under-19s in the UEFA Youth League earlier this month.
Losing such an incredible talent will be a disaster for United who are hoping to hang on to Gabriel despite his intentions to leave.