The Phillies say an MRI taken Tuesday at the Rothman Institute at Thomas Jefferson University Hospital revealed the strain. It is classified as a Grade 1/Grade 2 strain of the right calf.
Rollins suffered the injury during pre-game warm-ups moments before Monday's game against the Washington Nationals. The Phils say the DL stint is retroactive to April 13.
"We believe it to be a mild to moderate strain and we're hopeful it will be a two-to-four week recovery," said Phillies GM Ruben Amaro in a statement.
Infielder Wilson Valdez will take Rollins' spot on the 25-man roster. Valdez had his contract selected from triple-A Lehigh Valley.
The Phillies have gone 6-1 to open the season and Rollins is one reason why -- batting .391 with a .739 slugging percentage so far on the season.
It is the second time in his career that he has been placed on the DL. He previously spent time on the DL in 2008 with a sprained left ankle.
