The Cardinals on Wednesday announced that they've optioned shortstop Aledmys Diaz to Triple-A and called up 26-year-old Alex Mejia to replace him. To make room for Mejia on the 40-man roster, the Cardinals transferred right-hander Alex Reyes, who underwent Tommy John surgery earlier this year, from the 10-day disabled list to the 60-day DL.
As for Diaz, it's been a precipitous decline. In his rookie season of 2016, Diaz batted .300/.369/.510 with 17 home runs in 111 games and wound up making the NL All-Star team. He also showed skills growth on the defensive side as the season went along.