"He won't be available after these 15 days are over," said manager Ron Washington. "He hasn't picked up a ball yet."
Darvish could join the team in Houston or Kansas City on that trip, although there is also a chance he could miss all 10 games. Whether he needs a rehab start before returning to the Rangers has also yet to be determined. Darvish, who is 10-7 with a 3.06 ERA this season, is eligible to come off the disabled list Monday.
"He's going to stay here and continue to work and get treatment," Washington said. "I don't know how long he'll take to get started. He might be down for the whole 10 days."
Christian Corona is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.