Watson went down in training on Thursday and was immediately surrounded by the North Melbourne trainers. 

The 18-year-old was visibly suffering and was sent to scans by the medical stuff that unfortunately revealed the worst. 

Watson suffered an ACL rupture, keeping the second-round draft pick from last year out for at least the next 12 months. 

"There's the two types of ACL – the contact and the non-contact. This was a non-contact ACL," North Melbourne coach Brad Scott told radio station 3AW.

"It was a really innocuous, slight change of direction and his knee buckled and we all feared the worst – and that's been confirmed, unfortunately.

"So it's an ACL rupture and that will be 12 months (out) for Declan after his best game at North Melbourne (in the VFL) last week, so it's bitterly disappointing for him and for the club."