The Mets also said All-Star center fielder Carlos Beltran would sit out until the weekend because of a bone bruise below his right knee.
To fill the spots, the Mets promoted highly touted outfielder Fernando Martinez from Triple-A Buffalo and acquired journeyman infielder Wilson Valdez from Cleveland for cash.
"We've got to get back to being healthy," Mets manager Jerry Manuel said before Tuesday night's game against Washington.
The Mets began the day a half-game behind NL East-leading Philadelphia. New York has managed to stay close despite a string of injuries -- first baseman Carlos Delgado, catcher Brian Schneider, pitcher Oliver Perez and infielder Alex Cora already were on the DL.
Reyes has not played since last Wednesday, sitting out with an injured right calf. He tried to run before Monday night's game, but tendinitis behind the calf slowed him.
"This is hard. I haven't had injuries since 2004. Everybody knows the kind of player I am," he said. "I like to be in the field every single game.
"I'm not a player that needs to get to 100 percent to play. As soon as I can get to 80-85 percent, I'm going to be playing in the field."
Reyes' move to the DL was retroactive to May 21. He is hitting .279 with 11 stolen bases.
"We felt this was the best course of action," general manager Omar Minaya said. "We didn't see the progress from yesterday to today that we wanted to see."
Church missed his third straight start Monday because of a strained right hamstring. His move to the DL was retroactive to May 23. He is hitting .272 with one home run and eight RBIs.
Beltran had an MRI exam Tuesday that showed the bruise and an inflamed tibia, and a cortisone shot. After the series with the Nationals, the Mets are off Thursday and host Florida this weekend.
Beltran said he was relieved to know the injury wasn't something more serious involving his knee or hamstring, and said he was ready to play through the pain. He is hitting .367 with six home runs and 31 RBIs.
"I know I'm not going to feel 100 percent in three days," he said. "It's easier for me, knowing the issue."
The 20-year-old Martinez is considered the jewel of the Mets' farm system. He was set to start Tuesday night for New York, batting sixth and playing right field.
"When I get a young player, I like to put him in the lineup right away," Manuel said.
Martinez was batting .291 and leading the International League with 25 extra-base hits when the Mets selected his contract from Buffalo.
Valdez, who turned 31 last week, was hitting .198 at Triple-A Columbus after playing last year in Japan and Korea. In 111 games with the White Sox, Mariners, Padres and Dodgers, he hit .211 with one homer and 20 RBIs.