Sounds like Rangers tried to get Rios before the non-waiver deadline and they're trying again:
Rangers Claim Alex Rios; Trade Unlikely
by Steve Adams, Aug 8 at 4:51 PM CST
2:45pm: The Rangers are the team that claimed Rios, according to Evan Grant of the Dallas Morning News (on Twitter). Grant cautions that claiming Rios and actually striking a deal to acquire the 32-year-old are very different things.
12:58pm: Ken Rosenthal of FOX Sports reports that Alex Rios has been claimed on revocable waivers by an unknown team (Twitter link).
4:51pm: A trade is unlikely to be reached, writes MLB.com's T.R. Sullivan. Prior to the deadline, the White Sox were interested in lefty Martin Perez, right-hander Luke Jackson and infielder Rougned Odor, and the Rangers aren't keen on giving up those players in a trade for Rios.