The Nationals made a roster move to freshen up the bullpen prior to tonight's game against the Cardinals.
Cedeno was on a roll at Triple-A, having thrown 3 2/3 scoreless innings, allowing just one hit, walking one and striking out four.
Treinen made his major league debut earlier this month. He had three appearances with the Nats, totaling 6 2/3 innings and a 1.35 ERA.
The rookie Treinen threw 2 2/3 innings on Thursday against the Cardinals. He allowed seven hits and one run, walked one and struck out three batters.