An Islander first-rounder left town yesterday.

Forward Petteri Nokelainen, chosen 16th overall by the Isles in 2004, was shipped to the Bruins for center Ben Walter, the son of former Caps captain Ryan Walter, and a conditional second-round pick in 2009.

Walter, 23, has played 10 games for the Bruins since being selected in the fifth round (160th) of that same 2004 draft. The 6-foot-2, 200-pounder was named MVP for the Bruins’ Providence farm last season, second on the squad at 24-43-67 and a team-best plus-23 in 73 games.

Nokelainen, who played 15 games (1-2-3) for the Isles in 2005-06, spent last season in Bridgeport, 6-10-16 in 60 games.

“Ben Walter is a strong addition to our roster and immediately becomes one of our top prospects,” GM Garth Snow said. “Ben is a young player who will battle for a position in training camp.”