Mallinder was always an impressive young sportsman, comfortably taking to cricket and football while dad Jim spent three years as Sale Sharks head coach.
Unsurprisingly the Manchester-based side became the youngster’s team and not even a move to Northampton in 2007 could persuade Mallinder, then 10, to abandon his boyhood heroes.
However, five years later – and with a once fledgling football career now a childhood memory – he was approached to join the Saints Academy.
Fast forward two years and the inside centre led them to being crowned the country’s best academy side – ending their Exeter counterparts’ two-year unbeaten run at Allianz Park last month.
It has been a dramatic change of career path and allegiance for Mallinder, but the teenager insists he feels right at home.
“I grew up in Sale as a massive Sharks fan – that was my one team,” he said. “I watched people like Charlie Hodgson play and Jason Robinson.
“But when we were in Manchester I never played rugby – it was more cricket and football.
“I’m a big United fan and played in their academy for a season and it was really good fun – and I still play cricket.
“When we moved here I learned about the club, how it operates and I don’t think I could put myself playing anywhere else.”
Mallinder Snr has led Saints into one of the club’s most prosperous periods, reaching last year’s Aviva Premiership final and leading them into the weekend top of the table. And Harry cannot help but notice his dad’s influence around the club, whether directly or through others.
However, he believes he only stands to gain from having his old man at the top – and it doesn’t make his life any easier.
“You don’t see him too much but some of the lads make sure I’m aware he’s there,” said Mallinder.
“I got a bit of stick early on but it’s all light-hearted so I enjoy it. He keeps a good eye on me and makes sure I’m on point and I don’t get ahead of myself. I like that – that’s the way it should be.
“It means I’ve got to work just as hard, if not harder, than all the others but I’m pleased with how it’s going.”
Mallinder played much of his early rugby at fly-half, only recently moving to inside centre. A tall, powerful presence with a creative kicking game, it doesn’t take long to draw comparisons with England No.12, Billy Twelvetrees.
And with Twelvetrees’ latest Red Rose partner Luther Burrell also at Northampton Saints, Mallinder is hoping to develop the best qualities from Stuart Lancaster‘s Test centre partnership.
“I like playing in different positions – it can get a bit boring just stuck in one place,” he added.
“I look up to people like Luther and I want to play like him. I want to have both sides to my game. Billy is a great player and him and Luther are working really well together, so to be compared to someone like that is very kind.
“If I can get anywhere near what he’s achieved then I’ll be pleased.”