The Pirates also recalled right-hander Brad Lincoln from Triple-A Indianapolis to start the second game of the doubleheader.
Cedeno was hit on the back of his head while unsuccessfully attempting to break up a double play in the fourth inning of Friday's loss to Washington. Moments earlier, he extended his hitting streak to 10 games.
"He had limited symptoms initially, but got worse as the night progressed -- even after leaving the ballpark," Pirates general manager Neal Huntington said.
He was replaced on the roster by infielder Pedro Ciriaco, who was recalled from Indianapolis.
Cedeno was batting .252 with two home runs and 23 RBI in 79 games.
In six previous games with Pittsburgh this season, Ciriaco was hitless in six at-bats. He was batting .210 in 40 games with Indianapolis.
Lincoln was 6-7 with a 4.14 ERA in 14 starts in Triple-A. The Pirates made room for him by optioning reliever Tim Wood to Indianapolis.