Three Nationals minor league affiliates were scheduled to begin playoff series yesterday, but rain and flooding caused the postponement of two of them and the truncation of the third.

Class A Potomac was the only team that played, losing 5-1 to Frederick in a game shortened by rain to six innings. The P-Nats managed only three hits. Sandy Leon went 1 for 1 with a double and a walk. Steven Souza went 1 for 2 with a solo homer in the second that gave Potomac a 1-0 lead. Paul Demny allowed five earned runs in 5 1/3 innings on three walks and six hits, striking out five. He allowed four runs in the fourth inning.

Class AA Harrisburg, which won the Eastern League’s Western Division with an 80-62 record, had to cancel the first two games of its series. Instead of playing Games 1 and 2 at home, they will open Friday and Saturday at Richmond. Game 3 and Game 4 and 5, if necessary, will be played Sunday through Tuesday in Harrisburg.

Class A short-season Auburn, which won the New York-Penn League’s Pinckney Division with a 45-30 record, will attempt to start its series tonight in Auburn against Vermont.