Martin (biceps) is expected to begin a rehab assignment Tuesday or Wednesday, Shawn McFarland of the Dallas Morning News reports.
Martin, who has been in the 15-day injured list since April, made progress over the last week. He most recently threw a 25-pitch inning of live batting practice Saturday and is ready to rehab, likely at Triple-A Round Rock, which kicks off a series Tuesday against Sacramento. It's unclear how long Martin will need or if the Rangers will want him to throw on back-to-back days before activating the 39-year-old right-hander.