Tillman had soreness in his groin that put the start in jeopardy.
Triple-A Norfolk's Steve Johnson will undergo an MRI on his right shoulder in Baltimore after leaving last night's start after two innings with more discomfort. Johnson had been on the minor league disabled list with shoulder tendinitis.
"We came close to taking him and decided we wanted to let him have one more outing down there, make sure he's OK," Buck Showalter said. "I'm glad we didn't put him in harm's way up here. His velocity was down, too."
Showalter will miss Saturday's game to attend his daughter's graduation from law school at SMU, and third base coach Bobby Dickerson will miss Tuesday's game in Pittsburgh to attend his daughter's graduation. The Orioles likely will add director of player development Brian Graham to the coaching staff. Graham would coach third base in Dickerson's absence.
Graham served as the Pirates' farm director and interim GM.
Minor league infield coordinator Dave Anderson would be added if Graham can't work both games.
Showalter said Single-A Frederick catcher Steel Russell, son of Orioles' bench coach John Russell, may have broken his hand last night on a foul tip. Russell caught Parker Bridwell's near no-hitter.
OK, about the closer ...
Showalter was asked whether Tommy Hunter would work the ninth inning today in a save situation. Hunter gave up four runs in two-thirds of an inning last night and is 11-for-14 in save opportunities.
"I don't know yet. We'll see," Showalter said.
"I hope we have a three-run or two-run or one-run lead in the ninth inning today. I hope we have a four-run lead. That would be really nice."
Jim Johnson was given a long leash in 2014 while blowing nine saves, but he also registered 101 saves over the past two seasons before the Orioles traded him to the Athletics for infielder Jemile Weeks.
Showalter wants to avoid using a closer by committee approach, but he added, "I consider everything. What time of the night? Midnight, 1, 2, 3 or 4 or 8?
"It's not an advantage necessarily, but the difference between Tommy and Jimmy is, Jimmy had a track record. Tommy does, too, in certain other things. So there's some unknown with where we'll go with Tommy."
Here are the pitching matchups for the series in Kansas City:
Thursday: Wei-Yin Chen vs. Yordano Ventura
Friday: Chris Tillman vs. Jeremy Guthrie
Saturday: Bud Norris vs. Danny Duffy
Sunday: Ubaldo Jimenez vs. James Shields