Jerry Crasnick breaks down Los Angeles' options at closer with Kenley Jansen set to miss about a month because of an irregular heartbeat. (0:52)

Los Angeles Dodgers closer Kenley Jansen is expected to miss about a month with an irregular heartbeat, sources told ESPN's Buster Olney.

Jansen was placed on the 10-day disabled list Friday, and manager Dave Roberts said he didn't have a definitive timeline for Jansen's return.

Jansen missed about a month when he landed on the DL for the same issue seven years ago.

"I'm hoping as soon as I can to get something, just for my peace of mind, the guys on the field -- our peace of mind," Roberts said. "His health is most important. Whatever they have to do, the doctors have to do, to protect him.

"I know there are things out there as far as a timeline. I haven't heard definitive as far as any time."

The Dodgers said Saturday that Jansen will be reevaluated Aug. 20.

Jansen was at the team hotel before the Dodgers' game Thursday against the Colorado Rockies and didn't feel right. He was taken to a Denver hospital for tests and then sent back to Los Angeles for more evaluation.

When Jansen dealt with an irregular heartbeat in 2011, he was sidelined about a month because of his blood-thinning medication. Roberts said he wasn't sure if Jansen would need the medication again.

"If he does, that's a four-to-six week thing," Roberts said. "I'm not sure what the protocol is right now."

In 2012, Jansen was out again after suffering an irregular heartbeat during an Aug. 27 appearance in Colorado. He underwent a procedure on his heart on Oct. 23, 2012, to return it to normal rhythm.

Jansen, 30, is tied for the National League lead with 32 saves. In his absence, Roberts will use a closer-by-committee approach. Scott Alexander finished out the ninth in an 8-5 victory over the Rockies on Thursday.

"If I look at Scott right now, and look at our pen, he's our highest-leverage reliever," Roberts said. "At what part of the game is that most impactful to deploy him? That's kind of how I'll approach it. After that, to get the last three outs of the game, figure out who matches up best."

Roberts said all eight of his relievers are available to close on any given night.

"That's my story, and I'm sticking to it," Roberts said.

To take Jansen's place on the roster, the Dodgers recalled switch-handed pitcher Pat Venditte from Triple-A Oklahoma City. The 33-year-old Venditte has allowed four runs over 4⅓ innings in five appearances with the Dodgers this season.

The Associated Press contributed to this report.