The Cardinals optioned shortstop Aledmys Diaz to Triple-A and called up 26-year-old Alex Mejia to replace him, the club announced Wednesday. 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 made the NL All-Star team. He also showed skills growth on the defensive side as the season went along. Now he finds himself back in Triple-A thanks to a 2017 slash line of .260/.293/.396, which comes to an OPS+ of 80. Diaz still has some occasional home run pop, but he's just generating too many outs at the plate. 

The struggling Cardinals have been trying to address said struggles through roster churn. They've called up a somewhat steady stream of higher-rung minor-leaguers in response to injuries and underperformance. Earlier this season, they knocked outfielder Randal Grichuk -- he of the 24 home runs a season ago -- all the way down to Single-A so he could retool his swing. Grichuk recently returned to the active roster. Diaz will likely undergo a similar reconstruction. 

As for what's awry, these numbers tell part of the story ... 

Diaz in ...

Swing % on pitches out of strike zone

Rate of hard-hit balls

2016

26.8 percent

31.5 percent

2017

39.1 percent

23.5 percent


The big difference is that Diaz is chasing a lot more pitches this season, and as a result he's making weaker contact. "Don't swing at bad pitches" is advice that, particularly at the highest level, is easier to prescribe than implement. That's why bottom-up changes to swing mechanics and approach may be in order. 

More broadly, the Cardinals are clearly in no mood to let players work through their struggles at the big-league level. Despite an active winter and a seemingly impressive baseline of talent, the Cardinals are on pace for 87 losses. They're still within range of the NL Central lead, thanks to the prevailing mediocrity of the division, but nothing about this team carries the whiff of a contender right now. In a normal division, you'd argue for a trade deadline reboot, but the division lead remains tantalizingly close, even to a team like the Cardinals. 

Maybe a refurbished Diaz will help the cause? That seems to be the thinking in St. Louis.