The Single-A Potomac Nationals fell at Frederick 3-2 on Monday night, ending their defense of the Mills Cup.
Paul Demny took the loss (0-2) after allowing a pair of homers in a three-run first inning that set the tone for Game 5 of the Carolina League divisional series.
Demny allowed three runs in just 2/3 of an inning and is now headed to Florida on the instructional league roster.
Trevor Holder, Marcos Frias and Neil Holland held the Keys without a run or a hit for the final 7 1/3 frames, but it was not enough.
Jose Lozada RBI in the fifth got the P-Nats on the board, cutting the deficit to 3-1.
Brian Peacock drilled a solo homer with two outs in the top of ninth inning that cut the Keys' lead to 3-2, but Zach Walters struck out, ending the game. Walters had a double and scored the first run of the game for the P-Nats.
Frederick advances to the Carolina League finals against Kinston at home beginning Tuesday night.