"It's day-to-day," Redding said on Monday.
Redding felt some discomfort in his back as he began warming up during the bottom of the fourth inning of Sunday's exhibition game against the Marlins, but decided to gut it out because he was one of only six pitchers the Nationals brought to the game.
Most of Redding's pitches in that inning were left out over the middle of the plate, and the Marlins took advantage, tagging him for four runs.
The pain in Redding's back grew worse when he threw a pitch that went under the glove of catcher Paul Lo Duca for a passed ball. As Josh Willingham scored from third, Redding didn't even make it to cover home plate. He doubled over in pain and called for assistant athletic trainer Michael McGowan to come assist him. Manager Manny Acta and pitching coach Randy St. Claire also headed to the mound. A few minutes later, Redding left the game and was replaced by left-hander Ray King.
Redding says he can now move around without the sharp pain he felt on Sunday.
"I was able to extend and stretch that area out. I'm sitting around not doing anything. It's just kind of achy, but there is no sharp pain like there was yesterday," Redding said.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.