Yet such is the range of Hartson's developing talent that his appeal as a traditional centre-forward is not confined to those who like their number nines to be mean and muscular. The young bull that Arsenal will put up against the Spanish matadors in the Parc des Princes tonight can play a bit as well.
George Graham never had the slightest doubt, and while the fat lady was preparing to sing Graham's last song at Highbury, the manager's record of bringing on players from the lower divisions meant that his pay-masters did not balk at the prospect of paying Luton £2.5m, a record transfer fee for a teenager in only his second season of senior football.
That was in January. Less than six weeks later, Graham was forced to bid farewell to his most recent recruit along with the rest of the squad. It was a period of upheaval and uncertainty, and one which could have engulfed the 19-year-old's attempts to establish himself.
It also took Hartson back four years to when he was about to begin his career with Luton, only to discover that those who had taken the decision to offer him an apprenticeship had just been dismissed. Not surprisingly, Hartson was unsure what the future held.
What it held in the short term was a fair amount of physical distress, as the would-be star struggled to keep pace with fitness demands. It crossed his mind that he should jack it all in and return home to Swansea, and a disciplinary problem threatened to make that decision for him until David Pleat agreed he deserved a second chance.
Yesterday, Terry Westley, the Luton youth coach, recalled how tough it was for Hartson in the beginning. "He was on a big growth spurt at the time, and he found the running and the physical work really hard. Many would have washed their hands of him, but he never gave in, and when the ball came out it was obvious how much he loved to play. That won people over."
Now it is opposing defences who have to suffer for Hartson's growing pains. Weighing 14 stone, he is as strong as an ox and nothing fazes him. Just as the boy quickly became a man, so too did a prolific youth- team scorer quickly become a name to take note of in the First Division.
A goal illuminated his full debut against Nottingham Forest last season, but it was the impressive finish that prepared the ground for an FA Cup giant-killing over Newcastle that alerted a wider audience to the promise of the young Welshman.
Fastening on to a long pass, he delicately slid the ball past the advancing goalkeeper before calming squeezing home his shot. For an 18-year-old, it was a difficult task made to look deceptively easy, and it convinced his doubters that he possessed a big-time temperament.
Westley calls it "going cold"; the ability to shut out everything and apply maximum concentration to the art of striking the ball. "With some players, their speed takes them into scoring positions, but they are still moving at the moment of impact and the chance is wasted. That is why I think Andy Cole misses a few, because his head is on the up.
"John's eye-to-ball contact is excellent. I have seen him pick up a golf club for the first time and whack the ball 200 yards. That is timing, not power; the ability to keep your head still."
A winning goal in only his second game for Arsenal at Coventry immediately endeared him to his new supporters. He has looked equally at home in the European campaign, and a winner's medal against Real Zaragoza tonight would perfectly round off his first season for them.
"I've always had a great belief in my own ability and that has helped me to settle in," Hartson said. "I don't allow myself to worry about the pressures that might be on me, and while I was nervous when I first heard Arsenal wanted me, the moment I stepped into Highbury I was excited by everything I saw.
"Despite all the problems there have been, the spirit among the boys is tremendous. We desperately want to hold on to the Cup-Winners' Cup. If you have fought hard to win something, you don't let it go easily."
There is another battle he is desperate to win: the right to claim a regular place with his country. After a first performance against Bulgaria in March, many believe that will not be far away.
"He is passionate about Wales in a way I have never seen before," Westley added. "I was there when he made his debut for the under-18s, and it meant the world to him. In the five-a-sides he would always want to play Wales v England, even though it was him on his own against five others." Now wouldn't Vinnie, the honorary Welshman, just love him for that?