Coach Stephen Cunis commended the youngsters for their efforts, saying they really stepped up when it was needed.
He said the likes of Watson and Cooper pressured some senior Bay of Plenty players, which culminated in a collapse of seven for 37 on Sunday.
"Kurtley bowled consistently and, at the end, he had a bit more fire in the belly which played a big part.
"Henry Cooper made a few breakthroughs, even though he leaked runs he picked up wickets," Cunis told the Advocate, agreeing that the players' conditioning was obviously serving them well.
"Brad Kneebone again put in another gritty innings ... was gutsy and wore a few. He just guts it out and plays some classy shots among the grit."
The rise of the Northland youngsters, however, is not an accident. Cunis said club cricketers in the regionwere at a decent level, which was pleasing for the Northland coach.
"There are some decent club players out there who aren't even involved with Northland, which just shows the depth of our players."
Cunis acknowledged the win was a perfect start to the Fergus Hickey season, with the win also pushing Northland to the top of the Hawke Cup Challenger standings.
Of concern for Cunis was a sense of complacency at times, which triggered a collapse for Northland after Kneebone and Neal Parlane (59) had put the team in a strong position.
He added during Sunday's tea session he gave the team a short, sharp message to get the job done. "It was exactly what we wanted [as a result], but we went about it the hard way," Cunis said. "Then we let the foot off the throat.
"In the second session on Sunday, we bowled a four ball every over and it just wasn't good enough. There was a short, sharp message from me at tea and, credit to them, they went out with a bit more focus and purpose and picked up the last seven for 37."
Northland play a two-day fixture against Hamilton at the Cobham Oval next weekend.
Result: Northland 337 (Brad Kneebone 71, Neal Parlane 59, Kurtley Watson 45*) beat Bay of Plenty 287 (Watson 5/60, Henry Cooper 4/58).
Northland
Brad Kneebone, Henry Cooper, Dylan Lees, Tom Herman, Max Davis, Marc Lezar, Tome Smith, Neal Parlane, Cody Andrews, Kurtley Watson, Jason Morgan, Joseph O'Sullivan, Nick Stobart, Ben Hyde, Cam Johnston, Brandon Gilmour, Aaron Ashton, Ian Page, Joseph Yovich, Kieran Nelson, Dave Armitt, Tyler Lortan, Sam Walker, Brad Wilson, Rory Christopherson, James Marshall, Matt Taylor, Kevin Forde, Mike O'Flaherty, Kyran Dill, Findlay Buchanan.