Jose Altuve led off the game with the deep fly ball off Mariners right-hander Blake Beavan, and Saunders retreated to the wall and made an impressive catch, but his shoulder caught the wall flush. Saunders dropped to the ground, where he laid for several minutes while being attended by the team's medical staff.
Jason Bay replaced Saunders in the outfield and in the leadoff spot in the lineup.
Saunders was diagnosed with the sprain and will be re-examined by team medical director Dr. Edward Khalfayan. The Mariners said he is "expected to miss some time." For comparison, former Mariners outfielder Mike Carp also suffered a shoulder sprain while diving for a ball in the outfield on March 29 last season during the Mariners' Opening Day game against the A's in Japan. Carp didn't return to the Mariners until May 1.
In the meantime, the Mariners have a few options at Triple-A Tacoma, such as former Mariners outfielders Endy Chavez, Eric Thames and Carlos Peguero.
Doug Miller is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.