BALTIMORE -- The Orioles optioned struggling center fielder Cedric Mullins to Triple-A Norfolk on Monday, a move that restructures their outfield picture and the second significant roster shake-up in as many days.

The club’s Opening Day center fielder who debuted last season as the heir apparent to Adam Jones, Mullins hit just .094/.181/.156 in 22 games after slumping for most of Spring Training.

“We thought the best thing for him was to go down there and kind of clean-slate the season,” Orioles manager Brandon Hyde said. “His main thing is confidence. When you scuffle for a while, you can press. It gets mental. We just thought the best thing for him was to go down there in a different environment, a little bit less pressure and just go work on taking great at bats.”

Mullins started 17 of Baltimore's first 23 games in center field, where his offensive shortcomings were ameliorated by his defense. Mullins emerged as one of the Majors’ rangiest outfielders over the season’s first month. He rates among the game’s best in the Statcast metrics Outs Above Average (3, tied fourth) and catch percentage added (5, tied 11th), and made a highlight-reel game-saving catch to seal a win on Thursday against Tampa Bay. The Orioles do not have a true center fielder without Mullins in the field.

“That’s why it’s a little bit of a blow,” Hyde said.

In the interim, Hyde said reps in center would fall to Joey Rickard and Stevie Wilkerson, whose contract was purchased by Baltimore on Monday in a corresponding move. Rickard has made 49 appearances in center since 2016, while Wilkerson’s two professional games there both came this past week at Triple-A Norfolk. Rickard started in center and Wilkerson in left for Monday’s series opener against the White Sox.

From the trainer's room

• A day after leaving Sunday’s loss to the Twins with right quad tightness, Dwight Smith Jr. was out of the starting lineup for Monday’s series opener. Smith said he expects back in the lineup Tuesday, and he is healthy enough to come off the bench if necessary.

• The Orioles are re-evaluating Nate Karns after the right-hander left his first rehab start with right forearm tightness, Hyde said. Karns lasted just one-third of an inning in his appearance at Norfolk on Saturday, allowing three runs and walking two.

More concerning for the club was how Karns’ right arm responded following nearly two seasons lost to injury. After four appearances without allowing an earned run to open this season, Karns was placed on the injured list on April 9 when his fastball velocity dipped into the high 80s.

Down on the farm

On the heels of a banner first month at Norfolk, Orioles No. 2 prospect Ryan Mountcastle earned the International League’s Player of the Week honors on Monday. Mountcastle, 22, hit .370 with four home runs and 11 RBIs over seven games; he has hit .288 with a .865 OPS over 18 games thus far in 2019.

A converted shortstop who played third base in 2018, 15 of Mountcastle’s 17 starts this season have come at first base.

Worth noting

• Alex Cobb threw a simulated game Monday afternoon in lieu of his regular bullpen session, looking to shake off rust after struggling in his first start off from the injured list. Cobb approached the Orioles with the idea, then workshopped his stuff against Rio Ruiz. The righty matched a career high by allowing nine earned runs in Saturday’s 16-7 loss to the Twins.

“Cobber is his worst critic,” Hyde said. “He’s tough on himself.”

• John Means’ next start will come Wednesday in the series finale against Chicago, Hyde announced. The Orioles had originally hoped for Means to start again sometime after Thursday’s off-day, but last Friday’s rainout forced the club to adjust those plans. The left-handed rookie has been Baltimore’s most effective pitcher in the season’s first month, posting a 1.72 ERA across six appearances, including two starts.

• Right-hander Josh Lucas was designated for assignment to clear space on the 40-man roster for Wilkerson. Lucas allowed two earned runs in three appearances after joining the Orioles’ bullpen on April 11. When a player's contract is designated for assignment -- often abbreviated "DFA" -- that player is immediately removed from his club's 40-man roster, and 25-man roster if he was on that as well. Within seven days of the transaction (it was previously 10 days), the player must either be traded, released or placed on irrevocable outright waivers.