JUPITER, Fla. (AP) — Cardinals manager Mike Matheny isn't sure when first baseman Matt Carpenter will make his Grapefruit League debut.Carpenter is battling back tightness. For the time being, he is in the hands of the Cardinals' medical staff, who will determine when Carpenter can return to the field."When they are in their hands, we're following their lead," Matheny said. "They'll tell us."A three-time All-Star, the 32-year-old Carpenter missed much of last spring with back and oblique soreness.Matheny believes Carpenter's recent preseason injury issues can be attributed to his tenacious spring regimen."This is like Disney World for a baseball rat — spring training," Matheny said, "You come down, you can work all you want, the sun is shining, you use these beautiful facilities, you've got every single coach and every trainer at your disposal."The injury will at least force Carpenter to get some rest that Matheny said might help stave off fatigue later in the season."This could be one of those blessings in disguise," Matheny said.A career .277 hitter, Carpenter experienced a dip last year when he hit .241 with 23 homers and 69 RBIs. He is expected to bat third in St. Louis' lineup.At the moment, he isn't participating in baseball activities such as swinging a bat or fielding ground balls."We want to get him right," Matheny said. "We want to get him healthy, then we can figure out how to get his timing right."Jose Martinez, who hit .309 with 14 homers in 2017, would likely man first should Carpenter's injury linger longer than expected.Luke Voit started at first base for the Cardinals in their 6-4 Grapefruit League opening day loss against Miami on Friday.