Encarnacion has been bothered by the wrist since spring training, when he also was slowed by a sore right shoulder on his throwing side. He struck out in the ninth inning of a 4-1 loss to Houston on Monday night, extending his slump to 1-for-28.
Encarnacion appeared to aggravate the wrist in his last at-bat on Monday, prompting the Reds to send him for tests.
"You never know until you do the tests," manager Dusty Baker said. "I don't know if he did it on the last swing yesterday or before. I saw him wince in his last at-bat."
The Reds called up infielder Adam Rosales from Triple-A Louisville to take his spot. Rosales was batting .431 with four homers and 15 RBIs in 17 games. He played in 18 games for the Reds last season, batting .207 without a homer.
It was the first roster move of the season for the Reds, who also were missing left fielder Chris Dickerson on Tuesday.
Dickerson bumped heads with Houston shortstop Miguel Tejada while sliding into second Monday night. Dickerson left the game an inning later with a headache and dizziness. He was tested on Tuesday to determine if he suffered a concussion.
"I feel fine," Dickerson said. "No dizziness. I still have a little bit of a headache. My mental processing is a little hazy. I noticed that during the test."
Dickerson took a test that involved memorizing patterns and number sequences. He said one of his scores was significantly lower than when he took the test during spring training. Baker expects him to sit out the last two games of the series against Houston.
"He's feeling better, but he's not 100 percent yet," Baker said. "He's not doing too much activity."
Dickerson said he's had four concussions during his life. He ran into outfield walls in the minor leagues and in college. He also suffered concussions in grade school when he hit his head on the bottom of a backboard while trying to dunk, and when he was hit in the head by a tetherball pole.