It seems like it’s almost predetermined before the year begins that the St. John’s and Duxbury boys lacrosse teams are going to meet in the postseason with everything on the line.This season, however, the defending state champion Eagles were in serious jeopardy of not making the tournament. But wins in its last three games got the Prep a spot in the Division 1 East tourney and now, with a victory over Needham, the Eagles are heading back to Harvard Stadium for another round with the Dragons.On Saturday in Needham, Matt Scalise’s goal with 91 seconds left in regulation was the difference as the Eagles claimed a 10-9 win and reached their third straight state final meeting with Duxbury.The Dragons stunningly annihilated Grant Whiteway and No. 2 Billerica, 19-9, to set up a rubber match on Tuesday (7:45) in Cambridge.”If you asked us eight games in and we had a losing record if we’d be here, we weren’t sure what was going to happen,” St. John’s coach John Roy said. “The guys have battled all season long. They never gave up and stayed with it.”Saturday’s win was a true example of the Prep’s (14-7) stick-to-it-iveness. After running out to a 5-2 lead in the second quarter, the Eagles watched as Needham fought back and closed the gap to two at halftime.The Eagles reassumed a three-goal lead in the third quarter before Needham scored three unanswered times to deadlock things at 9-9 with 3:30 left.The winner came with 1:31 left as Blackwell set up Scalise perfectly for the senior’s fifth goal of the game. Needham would get a final chance, holding the ball in the final minute for a shot, but the Prep defense held firm.”We know that we have our work cut out on Tuesday,” Roy said. “Duxbury is a great team and playing them for a third year in a row in the finals is great.”