Can an opponent assign 4 damage to a single Watcher (with Sentry Deathknell) to prevent the draw trigger, even if it's non-lethal damage?

Ruling: Yes, an opponent can assign non-lethal damage to one unit as long as they only apply it to that one unit.

Nuances:

• This can be used strategically to prevent triggered abilities like Sentry Deathknell from activating by assigning all damage to a single blocker instead of distributing it.