CHICAGO - With utility player Chad Pinder going onto the disabled list with a strained left hamstring, the A’s called up top prospect Franklin Barreto on Saturday morning. The Chronicle reported Friday night that Barreto’s promotion was likely this weekend after Pinder left the team’s win over the White Sox in the fifth inning. The team had planned to bring him up next month after trade-deadline deals clear more roster spots and open up the second-base job for Barreto. The A’s everyday shortstop, Marcus Semien, has just started a rehab assignment at Class-A Stockton after missing two months with a wrist injury that required surgery.