Cain, 30, will return to San Francisco for further evaluation after an MRI exam revealed the strain, the team said. The Giants, who are in Phoenix playing the Diamondbacks, said he could miss two weeks. The DL move was retroactive to April 4.
Cain is the second Giants starter to be scratched from his opening start. Jake Peavy was unable to pitch Tuesday because of back stiffness.
New York Mets closer Jenrry Mejia was put on the 15-day disabled list because of inflammation in the back of his elbow. Mejia felt tightness in his elbow Monday night while warming up in the eight inning of the Mets' season opener against Washington and was unable to pitch in their 3-1 victory. He underwent X-ray and MRI scans and was given a cortisone injection Tuesday and was put on the DL retroactive to Sunday.
Indians' Carasco gets four-year deal
Two days after finalizing a long-term contract with ace Corey Kluber, the Cleveland Indians secured No. 2 starter Carlos Carrasco with a four-year, $22-million deal that includes club options for 2019 and 2020. Carrasco had a breakout season last year, going 8-7 with a 2.55 earned-run average in 40 games.
Milwaukee outfielder Ryan Braun had an MRI exam and was not in the lineup against Colorado, a day after leaving the Brewers' opener because of a strain in his right side.
Chris Davis returned to the Baltimore Orioles after missing their opener to complete a 25-game suspension for a positive amphetamine test.
Right-hander Rick Porcello agreed to a four-year, $82.5-million contract with Boston, which acquired him from Detroit in December.
St. Louis' game against the Chicago Cubs at Wrigley Field was postponed due to a forecast of rain and cold weather. A makeup date was not announced.