Morse went 0-for-3 with two strikeouts before leaving the game with a strained left calf. He suffered the injury while catching a sacrifice fly off the bat of Raul Ibanez in seventh inning. Morse is expected to miss a game or two and will be re-evaluated Thursday.
Morse tried to stay in the game, but the pain grew worse and he was replaced in right by Cristian Guzman in the top of the eighth inning.
Instead of using the platoon of Taveras-Willie Harris that was originally planned prior to the season, the Nationals plan to use a rotation of Harris, Morse, Taveras and Guzman. The team picked the Harris-Taveras platoon originally because they are sound defensive players.
But after getting pounded by the Phillies, 11-1, in their home opener Monday, the Nationals decided they wanted Morse's bat in the lineup. In his only at-bat in that game, Morse had a single.
Riggleman pointed out that Morse had a productive Spring Training, hitting .306 with two home runs and seven RBIs.
"Mike had a good spring. He has been swinging the bat well in batting practice," Riggleman said. "I spoke to our coaches. The Phillies have a left-hander going, and I just asked them what they thought. It could have gone one way or the other.
"Willy is a polished outfielder. I'm hoping we get some ground balls with [Nationals right-hander] Jason Marquis pitching. Maybe fly balls may not be that much of an issue. That's my hope. Maybe Morse may pop one for us in the gap. You never know."
The Nats have always loved Morse's bat. Last year, for example, the right-handed-hitting Morse was 6-for-19 with a team-leading eight RBIs as a pinch-hitter. During his career, he has a .324 batting average against left-handed pitching and .277 vs. right-handed pitching.
The right-handed-hitting Taveras, who went hitless in one at-bat Monday, signed a Minor League contract with the Nats last February knowing he could start the season on the bench.
Taveras said early in Spring Training that he would accept the role as a bench player even though he has been a regular for most of his career. In Spring Training, Taveras hit .298.
Harris started the opener in right field and went 0-for-4.
Also receiving an injury scare on Wednesday was reliever Jesse English. The left-hander was drilled on the right calf by a comebacker off the bat of Placido Polanco, but he said he was OK.