MILWAUKEE — Los Angeles Dodgers ace Clayton Kershaw received an epidural injection for his sore lower back and will be placed on the 15-day disabled list, manager Dave Roberts said before Thursday's game in Milwaukee.

"Clayton yesterday got an epidural, so at this point we're going to put him on the disabled list," Robert said. "And use the All-Star break, obviously, with the four days. And in the coming days, we should know more how that epidural . how he responds to that and that will give us some more direction."

Roberts did not know how long Kershaw is expected to be out, or who would make his scheduled start Friday at home against Colorado.

The three-time NL Cy Young winner is 11-2 with a 1.79 ERA this season. He lost his last start on Sunday night in Pittsburgh, giving up four runs and nine hits in six innings.

"He's been our most valuable player," Roberts said. "When you lose a player to the disabled list like Clayton, who you've counted on the fifth day start, obviously that's out of our control. I know Clayton's very disappointed, but it's up to us to pick him up."

The loss of Kershaw is another blow for a pitching staff beset with injuries. Starters Hyun-Jin Ryu and Brandon McCarthy are on rehab assignments coming back from surgery. Left-hander Alex Wood, who went on the disabled list on May 31 with an elbow problem, was transferred to the 60-day DL on Wednesday.

Brock Stewart, who opened the season at Class A, made his first big league start Wednesday night. Julio Urias, 19, has made three starts since being called up May 27, picking up his first victory in the series opener on Tuesday night.

"It happens to every team, injuries, and we've been bit by the injury bug," Robert said. "Your best player, to deal with this, it's a big blow, but we've got to keep moving forward."

Kershaw has been on the disabled list only once in his nine-year career, in early 2014 with a shoulder strain.