Miguel Montero says he apologized to Jake Arrieta after criticizing the Cubs pitcher for allowing seven stolen bases in a 6-1 loss to the Nationals. (1:11)

WASHINGTON -- The Chicago Cubs on Wednesday designated catcher Miguel Montero for assignment, one day after he publicly called out starter Jake Arrieta for allowing seven stolen bases by the Nationals in a 6-1 loss Tuesday night.

On Tuesday, the catcher criticized Arrieta and the Cubs pitching staff for the Nationals' baserunning success, saying: "That's the reason they were running left and right today, because they were slow to the plate. Simple as that. It's a shame it's my fault because I didn't throw anyone out."

Speaking Wednesday, Montero said he apologized to Arrieta, and the right-hander told reporters that the two were on good terms.

But Cubs president Theo Epstein and manager Joe Maddon both said Montero's comments necessitated a roster change.

"When something goes wrong on the field, we expect our players to take the blame, step up and proactively assume the blame for it, even if it's not their fault," Epstein said. "That's the way to be a good teammate. He completely agreed when it was pointed out to him and he apologized.

"After thinking about it some more, I just came to the conclusion that now more than ever we need to be a team. This was an example of being a bad teammate publicly and that we'd be better off moving on and not standing for it."

Added Maddon: "Regardless of Jake saying it would not have impacted the clubhouse, I think it would have. There are too many young guys in there that are impressionable. You don't want to foster, nurture or condone that kind of message."

Montero, who had a huge hit late in Game 7 of the World Series last year, hasn't thrown out any of the 31 potential base stealers against him this season, according to ESPN Stats & Information. He was hitting .286 with four home runs and eight RBIs in 44 games.

In an appearance on ESPN 1000 Chicago earlier Wednesday, Montero said he took responsibility for his comments and apologized to Arrieta.

"I called Jake to apologize," Montero said. "It was the heat of the moment. He's grinding out there; I'm grinding behind the plate. It's tough. It's the heat of the moment. I said what I said -- yes, I'm responsible. I talked to him to apologize because I feel like I should step up and apologize, and I did."

Montero added: "Jake was totally fine [with the apology]. He actually agreed with me. We're cool. He was totally cool."

Arrieta, speaking later Wednesday, said he was OK with Montero and added it was sad to see him go.

ESPN Staff Writer Watch Jake Arrieta discuss the situation with Miguel Montero.

Before his radio appearance, Montero tweeted his reaction to leaving Chicago, calling Cubs fans the "greatest" and saying it was an "honor to play" for the organization.

It's not the first time Montero, 33, has spoken out.

On the day of the Cubs' parade to celebrate their World Series championship last season, he was critical of how Maddon used him throughout the year while also questioning communication between the two. A spring training dinner cleared the air, but apparently Tuesday was the last straw. After hearing his comments Tuesday, teammate Anthony Rizzo fired back at Montero.

"We win as a team, we lose as a team," Rizzo said during his weekly appearance on ESPN 1000 Chicago. "If you start pointing fingers, that just labels you as a selfish player. I disagree. We have another catcher [Willson Contreras] who throws out everyone who steals, and he [catches for] Jon Lester who doesn't [throw] over. It's no secret. Going to the media with things like that, I don't think it's very professional."

The Cubs called up Triple-A catcher Victor Caratini to take Montero's place. Caratini is hitting .343 with 20 doubles, 2 triples, 8 home runs and 54 RBIs for Iowa.