Even before the rebuilding Astros traded veteran shortstop Jed Lowrie and the organization’s MLB-low payroll took another hit, the team was staring at holes in several key areas. The outfield, the back end of the starting rotation and the bullpen were completely up for grabs heading into spring training, while third and first base weren’t officially locked down. The Lowrie deal strengthened the Astros at first. Houston sees real MLB potential in Chris Carter, one of three prospects acquired from the Oakland Athletics for Lowrie. Carter, 26, had 16 home runs and 39 RBIs with a .514 slugging percentage in 218 at-bats last season for the AL West champion A’s. [...]