Ventimiglia told The Associated Press during a telephone interview Wednesday that he hopes Nathan's death is far from final.
"I really hope he's not going anywhere," Ventimiglia said. "That would be really disappointing to me to lose a brother and an amazing scene partner. I'm sure it's all going to work out the way it's supposed to."
Ventimiglia says he didn't watch the finale - and he wasn't alone.
Ratings for Monday's episode were down from the previous week, and the conclusion of Volume Two was the lowest-rated finale episode for the show yet, according to Nielsen Media Research.
Meanwhile, the actor doesn't know anything about future scripts in light of the writers' strike: "We ran out of stuff to shoot. That's basically what it boils down to."
Ventimiglia says he'll appear in the upcoming films Game and The Chaos Theory.
"I try and take a break and take a vacation," he said. "But I keep getting wrapped up in jobs."