Derek Holland has been officially activated from the 60 day disabled list and added to the active roster for his start tonight. To clear a 40 man roster spot for Holland, the Rangers have recalled Shawn Tolleson from AAA Round Rock and placed him on the 60 day disabled list.
Tolleson was on the minor league disabled list due to back problems, and given his struggles this year and his current injury, it appeared unlikely he was going to be looked at as a viable bullpen option in the majors the rest of the way. This means Tolleson's major league season is over, though I guess he could theoretically still pitch in the minors on a rehab assignment, if he's healthy enough at some point to do so. Tolleson to the 60 day d.l. was one of the options we thought was likely to clear a 40 man roster spot.
More surprising, however, is the news that Josh Hamilton has been activated from the 60 day disabled list and placed on release waivers. That doesn't clear a roster spot, and Hamilton was already ruled out for the year due to his knee surgery, so I'm not sure what purpose it serves doing this now. Hamilton was expected to be released this offseason, with the team looking to re-sign him to a minor league deal in the offseason.
UPDATE -- Jon Daniels says that "given the rules in place" releasing him now allows them to the possibility of "extending the relationship" in the future. I don't know if the Rangers would be barred from re-signing him if they released him after the season, or what. But that's the explanation we have.
UPDATE II -- Per Evan Grant, the Rangers had to release Josh before September 1, or else they would have been barred from having him playing for them in the majors prior to May 15, 2017. The possibility of Hamilton being in the majors next year prior to May 15 seems remote, but that at least clarifies why the decision was made to release him now.