BOSTON -- For weeks, the Red Sox have talked about the need to improve their shaky defense.

On Tuesday, manager Alex Cora took some action, announcing that Kiké Hernández will no longer be the team’s primary shortstop and rookie first baseman Triston Casas will likely see his time reduced in the field.

The news came one day after Hernández increased his MLB-leading errors total to 14 -- with 13 coming on throws -- with a key miscue that cost the team a run in a 4-3 loss. Casas also mishandled a routine grounder with two outs in the 10th inning that allowed Colorado to score what wound up being the decisive run of the game.

“[Hernández] is going to play less short,” said Cora. “We’ve got to be better defensively. That’s the bottom line.”

For Tuesday’s game against the Rockies, Pablo Reyes made the start at shortstop with Justin Turner playing first base. Casas started at DH, while Hernández was on the bench.

“We went with our best defensive alignment. If there’s a book about baseball, that’s rule number one: You play bad defense, you don’t win games,” said Cora. “That’s the bottom line. When you give the opposition more than 27 outs, they’re going to cash in, and we can go back the last 10 days, when certain plays that we didn’t make gave the opposition an extra run."

Entering the night, the Sox had a 33-34 record while making 47 errors, the second-highest total in MLB.

Cora said that for the time being, Hernández will get most of his playing time at second base and center field, but that he will also be a late-game replacement at short when the team hits for Reyes.

Boston’s Plan A for this season was for Trevor Story to be the starting shortstop. Story played a stellar second base last season, and when Xander Bogaerts left as a free agent, it seemed like a golden opportunity for Story to go back to the position he’s played for most of his career.

But that changed when Story had to undergo an internal bracing procedure on his right elbow in January. The athletic veteran said Monday that he should be ready to play shortstop for the Red Sox by August.

Once Story went down, Hernández was given the opportunity to play shortstop, a position at which he had started 64 career games prior to this season. Hernández expressed confidence in his ability to be able to play the position on a near-everyday basis, but he struggled with his throws from the outset of the season.

The Red Sox rank 27th in the Majors in outs above average at shortstop at minus-seven.

Cora said Hernández’s biggest trouble spot has been on plays to his right.

“He has a good arm. He has good mechanics,” said Cora. “We’ve been surprised. He’s surprised. It’s not a lack of work. “

Yu Chang, a highly rated defender at shortstop, should help when he returns from a fractured hamate bone in his left wrist. But Chang was recently pulled off his Minor League rehab assignment due to recurring soreness and is probably a minimum of 10 to 14 days away from playing for the Red Sox.

As for Casas, he was impressive on defense during his September callup last season, but he hasn’t had the same consistency so far this season.

For now, that could lead to Turner playing more first with Casas at DH. The Sox are 22nd in the Majors in outs above average at first base at minus-three. Casas started 51 of the team’s first 67 games at first.

“There are a few things we have recognized,” said Cora. “This kid, when he came up last year, we thought he was going to be a great defender, and there are a few things he’s not doing, so we’re working with him as far as his pre-pitch and some things we have to clean up with decisions on ground balls, and we’ll keep working with him just like we’re working with Kiké. 

“I told Kiké this is not the end [of him playing short]. It’s just something we have to do for now, but we’re going to keep working on his angles and throwing and all that, and we’re doing the same thing with Triston.”