SURPRISE, Ariz. -- Rangers relievers threw live batting practice on Thursday, but rookie right-hander Luke Jackson remains sidelined with stiffness in his lower back. Jackson told the medical staff this has been a minor issue in past springs, but the Rangers want to make sure.
"We are disinclined to pass it off as minor," assistant general manager Thad Levine said. "We want to confirm that, so we are going through the battery of tests right now."
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Jackson, the 45th pick in the 2010 Draft, appeared in seven games last season for the Rangers, sporting a 4.26 ERA. Opposing hitters went 5-for-25 off him. A starter through his first four professional seasons, Jackson was moved to the bullpen in 2015.
Jackson has an uphill battle to win a spot as a right-handed setup reliever against Sam Dyson, Keone Kela, Tom Wilhelmsen and Tony Barnette.
• Reliever Tanner Scheppers underwent surgery on Wednesday to have damaged cartilage removed from his left knee. He will not be able to put weight on it for six weeks and is expected to be sidelined until after the All-Star break.
• Shortstop Elvis Andrus on the new rules cracking down on runners trying to break up double plays at second base: "I love it as a fielder, but hate it as a runner."
• Yu Darvish, recovering from Tommy John surgery, will throw off the half-mound in his next bullpen session. Levine said the Rangers have yet to determine when Darvish will be able to throw off a full mound.
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.