Castillo allowed an unearned run in the first inning, then blanked the Mets for the next six innings on two hits. He didn't issue a walk and struck out 10.
The Phillies put away the game early by scoring three in the bottom of the first and adding four in the second. Outfielder Brian Gump, designated hitter Pat Murray and first baseman Chris Duffy drove in two runs apiece. Gump had a pair of doubles and scored three times.
The best-of-three championship round, Phillies vs. the Rays, begins on Tuesday afternoon. The Rays advanced to the championship round by beating the Marlins, 1-0, in 10 innings.
Roly deArmas' Phillies struggled down the stretch of the regular season, losing their final three and five of six, but they hung on to finish on top of the North Division (32-24).
Larry Shenk is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.