"He'll go to the top," said Nelsen, a former centre back of some renown himself. "I had to buy (West Ham manager) Sam Allardyce a couple of bottles of red just to get him back, to tell you the truth.
"No he'll go to the top, there's no question about that. He's got all the tools."
Allardyce, who managed Nelsen at Blackburn Rovers, saw that firsthand in the off-season when Toronto FC sent the 21-year-old Henry to London to train with the Premier League team.
It speaks volumes about Henry — and the unwavering support of his Toronto FC boss — that Nelsen offered the glowing endorsement three days after a pair of missteps by Henry led to two goals in a 2-1 loss to the New England Revolution.
The first, an errant pass set the stage for a long-range rocket from Patrick Mullins, a candidate for MLS's goal of the week. The second, a handball in the box, produced a penalty and the winning goal from Lee Nguyen in the 82nd minute.
Henry, who took more than his fair share of stick from the media, put his hand up afterwards and took the blame.
"As a defenders, we're always put in situations where were going to be blamed for goals. But you know what, it takes big players with big character to own up for their mistakes," said Henry.
His manager had his back.
"Look, this is professional football," said Nelsen. "When you make a mistake which led to the goal, that's what everybody remembers."
In truth, Henry's giveaway was not Toronto's first of the match. It was just punished by a world-class strike.
"He just took a wrong option," said Nelsen, before pulling out one of his favourite expressions. "If he had kicked the ball into Row Z, nobody would have remembered it.
"But these are the learning pains that young centre backs have to go through. (Chelsea's) John Terry, (Manchester United's) Rio Ferdinand, all of them do it. All of them have gone through it. I went through it myself at that age. You've just got to get them out of the system and you learn."
It's debatable whether a Cirque du Soleil contortionist could have got his body out of the way on the handball play against New England. Although it can be argued Henry was overly optimistic in putting his body in such a situation.
The six-foot Henry is an athletic specimen. He has power and pace, able to step up quickly to intercept the ball and blunt attacks.
At times, that athleticism leads him to trouble as he bites off more than he can chew.
Henry is a good fit with defensive partner Steven Caldwell, a hard-nosed 33-year-old Scot who has been round the soccer block.
Caldwell, while he has good acceleration in short bursts, relies on his experience and positional savvy.
Both have benefited from a steady backline. Injuries aside, Caldwell and Henry have been flanked by fullbacks Justin Morrow and Mark Bloom this season in a cohesive unit.
Henry missed all of April with a knee and calf injury suffered against Real Salt Lake on March 29. English veteran Bradley Orr, who has played most of his career at fullback, filled in admirably but Nelsen put Henry back in as soon as he was healthy.
While some only see mistakes, others see Henry as a future captain for both club and country.
For Nelsen, the way Henry responds to mistakes proves his mettle.
"The difference between the ones who don't make it and the ones who make it are the ones who get back on he bicycle and keep on going."
While Henry admitted his errors, he also saw the big picture.
"Fault me for my mistake but other than that I was pretty solid."
Henry became the first player from the Toronto FC Academy to graduate to the first team when he signed a pro contract in August 2010. Just 17, Henry had already made three appearances for the senior side.
He has 11 caps for Canada, including 10 starts. Plus 53 league appearances for Toronto.
That experience, along with the training stint in England, has boosted Henry's confidence on and off the field. He wears a smile and confidently interacts with the media, whereas before he offered little.
Put a box of new soccer shoes in front of him and the poised professional turns back into the big kid, however.
Henry is both as his soccer journey begins to get really interesting.
"Mentally I think I'm in a strong place," he said.
"I'm no longer going to use experience as a factor," he added. "I'm ready."