The encouraging statistic for Newcastle United fans is that their new signing Aleksandar Mitrovic scored 36 goals in his two seasons at Anderlecht. The worrying statistic is during that time he picked up two red cards and 13 yellows. He is big, explosive and talented but there is a streak of wildness. Perhaps it is only natural, given he is 20, but there are times when he can seem rather younger than that.

If Mitrovic on the pitch is tough, passionate, committed and no stranger to controversy, off it he often seems as though he is on some sort of standby setting. He walks and talks slowly, and spends most of his time outside football with his family, his girlfriend, Kristina, or watching television.

His regular changes of outlandish haircut – “life’s boring enough without always having the same hair,” he says – should not be taken as an indication he is some kind of peacock or playboy. The comparison to Mario Balotelli was made early in his career but it is one Mitrovic rejects. “Balotelli is not my role model,” he said. “I like him as a player very much and he is very talented. He could have been at the very top but my style does not have anything with him.”

His models, rather, are Didier Drogba and, more recently, Diego Costa. “He runs, scores, defends, is passionate and is a team player,” Mitrovic said of the Spain international. “I want to be like that.”

Effort certainly is not an issue. Mitrovic’s fitness coach, Andreja Milutinovic, who worked last season with Internazionale, describes him as one of the most professional players he has worked with, saying Mitrovic has never been late for training and has his own programme he follows outside of team practices. The Serbian journalist Aleksandar Stojanovic once joined him in training at Partizan and was struck by his silent concentration lifting weights and then in hill sprints in Kosutnjak forest in Belgrade.

Despite that, there was a time when Mitrovic was accused of being overweight; the result, it turned out, of his mother’s cooking. More recently, he reportedly returned to Anderlecht from international duty apparently the worse for wear from, it was said, having stuffed himself with pizza. He has switched to natural shakes, introduced more fish to his diet and tries not to eat too late at night to keep his body fat down. The fact is, though, as he himself acknowledges, he likes to eat and, for all his efforts in the gym, he seems to be somebody who puts on weight easily.

Eating aside, however, there is a single-mindedness about Mitrovic, a will to win perhaps best seen at the European Under-19 Championship in 2013 when Serbia beat France in the final and he was named player of the tournament. “He is dedicated to the team,” said the then coach, Ljubinko Drulovic. “Did you see him in the final coming back to our penalty box when France were attacking – not a set piece but during open play? He is a team player. He likes to win. He even criticised some players for not doing their duties in defence, saying to one: ‘If you don’t follow your full-back again I’ll come and beat you up, understand?’”

Alongside that there is a recklessness, a thoughtlessness, a hot-headedness that can get him into trouble. Mitrovic scored against Borussia Dortmund last December and celebrated by sticking his tongue between index and middle fingers, a gesture that was widely condemned for being sexually suggestive. “It’s personal,” he said. “I don’t want to talk about it but it’s not what they think. They should have asked me about it and now, as they did not, and they have accused me, I don’t want to speak about it.”

It has been suggested that what he was actually miming was cutting the tongues of his critics. Not there have been too many of them. Belgian journalists seem to have regarded him with affection, as a big likable kid who occasionally does something a bit daft.

In another Champions League game, against Paris Saint-Germain the previous season, Mitrovic and the midfielder Luka Milivojevic clashed with Zlatan Ibrahimovic. “He swore at us in Serbian,” Mitrovic said. “What did he think we were going to do? Back off?”

Backing off is something he has never done. Mitrovic is aggressive and self-assertive, somebody who works ferociously hard – even if he occasionally eats a little too much. He’s got the physique and the technical ability and if at 20 he is a little gauche, so what? Far more important, surely, is that he has a determination and an edge.

He is far from the finished product but there is plenty of raw material to refine.