BALTIMORE -- Adalberto Mondesi will begin a rehab assignment with Triple-A Omaha on Tuesday, but the Royals do not have an official timetable for his return from the left shoulder subluxation that’s kept him out since July 17.

Kansas City manager Ned Yost said the shortstop is going to be in the designated hitter role on Tuesday, and then play three to five innings twice. After that, the team will determine if Mondesi needs a day off or if it will put him back at DH the following game.

The Royals’ series opener with the Orioles on Monday was the 30th game Mondesi has missed since the injury. The team is being cautious.

“We’ll wait and see,” Yost said. “We’ll see how he goes. We’re in no hurry to rush him back. [We] need to make sure he’s good.”

The 24-year-old Mondesi sustained the injury when he tried to make a diving catch on the Kauffman Stadium warning track. Still, despite missing just over a month, he remained tied for first in the Major League in triples (nine) and second in steals (31) heading into the series in Baltimore.

Duffy to pitch simulated game

The plan for injured pitcher Danny Duffy (strained left hamstring) to throw a simulated four-inning game with ups and downs on Tuesday in Baltimore remains in place. He was placed on the injured list on Aug. 6, retroactive to Aug. 4.

"We'll see how he does tomorrow," Yost said on Monday. "He's going to go four ups and downs. He's going to go four innings and limit his pitch count to around 15 per inning. We'll see how he does, and go from there."

Worth noting

• Center fielder Bubba Starling is matched against a former high school teammate in this series. O's starter John Means and Starling played two years together at Gardner-Edgerton High School, about 35 miles from Kauffman Stadium.

• Yost celebrated his 65th birthday on Monday, and the Royals likely want to give him a win.