Matt Harrison threw today for the first time since May, 2014, and reported that his back is fine, according to Jeff Wilson on Twitter.
Harrison has missed most of the past two seasons with back issues, and underwent back fusion surgery last summer. There are questions about whether he'll ever be able to pitch in the majors again, but Harrison is working to try to get back on the mound and perform for the Rangers in 2015. The team is opting to have him take things slowly, and he most likely will start the season on the 60 day disabled list, allowing him to work his way back gradually and have a full rehab stint in the minors.
The loss of both Harrison and Martin Perez for most of last season, and the start of 2015, has ripped a gaping hole in the rotation, which the team is attempting to patch (for now) with Ross Detwiler and, most likely, either Nick Tepesch or Nick Martinez. If Harrison can return and be a productive rotation member for the Rangers by the middle of 2015, that would be a huge shot in the arm.