Dioner Navarro’s work ethic was factor in decision to let him go

Turns out Dodgers Manager Don Mattingly wasn’t kidding when he talked about the kind of effort he expected from his players.

The rookie manager said Friday that the “philosophical differences” he had with the departed Dioner Navarro concerned the catcher’s work ethic — or lack thereof. Navarro, who was on a one-year, $1-million contract, was designated for assignment Tuesday.

“I believe in work, very simple,” Mattingly said. “I believe you have to work and work and work — and that’s if you’re going good. I don’t care who you are. Matt Kemp … has to keep getting after it. I just believe in that.”

And Navarro was no Kemp with the bat in his hands, batting .193 in 202 plate appearances.

Navarro’s defense had also become an issue, in particular his throwing and blocking of pitches in the dirt.

While saying he liked Navarro personally and didn’t want to denigrate him, Mattingly acknowledged he was dissatisfied with Navarro’s mental and physical preparation.

“It’s not just physical,” Mattingly said. “It’s being ready to play every day.”

Mattingly said he had spoken to Navarro about the problems.

“We were all up front,” Mattingly said. “We didn’t hide anything. We had talked about some of the issues we’d had awhile back, the way I felt about it. It got to a point where it was time.”

In fact, Mattingly said the Dodgers might have let go of Navarro sooner had Rod Barajas not been injured last month.

Jansen back

Exactly a month removed from his last major league game, Kenley Jansen was on the Dodgers’ active roster again.

“That was a long time,” said Jansen, who was prohibited from competing while on blood-thinning medication to remedy a heart problem.

Jansen continued to throw regularly while sidelined, and he said the time off allowed him to develop his secondary pitches. The hard-throwing reliever said he sharpened his slider and started working on a changeup.

Jansen said he threw a changeup in one of the rehabilitation appearances he made with Class-A Rancho Cucamonga.

“I threw one and got a swing and miss,” he said.

But has he worked up the nerve to throw the pitch to a major league hitter?

“No,” he said, smirking. “I’ll keep working on it.”

Short hops

Roger Arrieta, who organized a rally in July to protest Frank McCourt’s ownership with the Dodgers, is leading another march Saturday. The rally is scheduled to begin at noon at the intersection of Sunset Boulevard and Elysian Park Avenue. … Utility infielder Jamey Carroll was placed on waivers by the Dodgers, according to a baseball source who spoke on the condition of anonymity because he was unauthorized to speak on the matter. … First-round pick Chris Reed made his professional debut Wednesday, pitching two scoreless innings for Rancho Cucamonga.

dylan.hernandez@latimes.com