Per Richard Durrett, Adrian Beltre's MRI showed a Grade 1 strain of his hamstring. Grade 1 is the least severe grade, but it is still serious enough that Beltre has been placed on the 15 day disabled list.
Chris Davis, meanwhile, will be called up to replace Beltre on the active roster. It is likely Davis's last chance in Texas to show that he belongs in the big leagues, although Davis's numbers in the majors so far this season haven't been bad:
Davis has been putting up video game numbers in AAA, posting a .368/.405/.824 line with 24 home runs in 210 plate appearances, and playing third base and left field.
Davis will likely replace Beltre as the team's starting third baseman while Beltre is out.
UPDATE -- Davis is playing 3B and batting 8th tonight.
UPDATE II -- Per various folks on Twitter, the Rangers expect Beltre to miss two to three weeks.