The Dodgers optioned Bobby Miller to Triple-A Oklahoma City this afternoon. Los Angeles recalled reliever Ricky Vanasco to step into the bullpen for the time being.

Miller was the Dodgers’ most reliable starting pitcher by the end of his rookie season. The former first-round pick and top prospect turned in a 3.76 ERA over 23 starts in his debut campaign.

He entered this year as the arguable #3 arm behind offseason pickups Tyler Glasnow and Yoshinobu Yamamoto. Miller’s year could hardly have started any better, as he tossed six scoreless innings with a career-high 11 strikeouts against the Cardinals in his debut.

Things fell off after that. The Cubs tagged Miller for five runs without allowing him to escape the second inning during his next start. Miller came out of his third appearance with shoulder inflammation. He spent the next two months on the injured list.

The Dodgers activated Miller from the IL on June 19. He has taken the ball four times since that point with dismal results. Miller allowed five runs over 6 1/3 frames at Coors Field.

He surrendered three runs over two innings to the White Sox before tossing five frames of two-run ball against the Diamondbacks. Working on a full week of rest, he hit a low point in last night’s start against the Phillies.

Philadelphia tagged Miller for nine runs on 10 hits through four innings. He gave up two home runs and has surrendered at least one longball in each of his last four outings.

Miller has issued three walks in every appearance since returning and hasn’t recorded more than four strikeouts in a start. Since his reinstatement, he has allowed 19 runs across 17 1/3 innings. Miller has walked 12 while striking out nine. Opponents are hitting .338/.434/.620 with five homers in 83 plate appearances.

That’s obviously nowhere near the level the Dodgers were expecting. Miller and skipper Dave Roberts each told reporters that the pitcher is not working through any shoulder discomfort.

Miller has lost a bit of velocity, though, sitting in the 96-97 MPH range with his fastball after averaging around 99 MPH during his season debut. It’s possible there’s something amiss mechanically, although a 96-97 MPH heater should still have plenty of life.

Pitchers must spend at least 15 days in the minors after being optioned unless they’re recalled to replace an injured player. The Dodgers can bring Miller back up on July 25.

That could amount to skipping just one turn through the rotation because of next week’s All-Star festivities, but Roberts said the team doesn’t have a specific target for Miller’s return. It’s not out of the question he remains in Triple-A past the July 30 trade deadline.