The Cubs reinstated Rios (groin) off the 10-day injured list Saturday and optioned him to Triple-A Iowa, Taylor McGregor of Marquee Sports Network reports.
Rios has struggled mightily in the majors this season, slashing just .071/.235/.214 across 34 plate appearances. His OPS jumps up to .781 in Triple-A, but it's unlikely he gets many more opportunities in the big leagues unless he shows improvement in the minors.