Upper Darby sure knows how to win in dramatic fashion.

Steve Thiesen drilled a walk-off RBI double in the bottom of the eighth inning to give the defending champion Blue Sox a 6-5 come-from-behind victory over Springfield in Game 1 of the best-of-5 Delco League semifinals.

Game 2 is Tuesday night at Cardinal O’Hara (5:45 p.m.).

The second-seeded Blue Sox rallied from a 5-0, first inning deficit to take the series opener. Gabe Encarnacion, Reed Farrell and Connor Scanlan drew consecutive walks with the bases loaded to give the Colonials a 3-0 lead. Tom Crumlish followed with a two-run single to extend the lead to 5-0.

Christian Strickland ripped an RBI single and Andrew Yates followed with a three-run homer in the third inning to get Upper Darby within 5-4. Yates singled in the tying run in the bottom of the seventh inning.

Yates finished 3-for-4 with four RBIs and one run scored. Andrew Fine added three hits and two runs scored. Crumlish paced Springfield with two hits.