Hunter was scheduled to start on Wednesday, but that changed when he warmed in the bullpen during Tuesday's 14-inning win against the Mariners. He threw roughly 30 pitches but did not enter the game. As a result, Baltimore pushed him back four days.
"We just didn't feel comfortable for Tommy, after getting fully hot [Tuesday] night to come in that game, which he had to do, that it was fair to start the game," Orioles manager Buck Showalter said.
Hunter has not started since Aug. 3 and will take the place of Zach Britton in the O's rotation. Britton was optioned to Triple-A after Tuesday's win.
The Orioles are 4-2 on their current 10-game homestand. They will face Bruce Chen on Sunday. The left-hander is familiar with Camden Yards, pitching for Baltimore from 2004-06.
The Royals won, 7-3, on Saturday and took the Thursday's opener, 8-2. Chen will look to win his ninth game and clinch a series win for Kansas City.
Chen will make his 26th career start at Camden Yards, where he is 7-6 with a 4.76 ERA. He beat the White Sox in his last outing, giving up two runs on seven hits in 6 1/3 innings on Tuesday. That quality start followed one of his worst performances of the year, when he allowed four runs in 2 2/3 innings against the Indians, prompting him to be more aggressive in the strike zone.
"His last three or four starts, he comes out and he hasn't established his fastball," Royals manager Ned Yost said. "All he's doing is throwing 82, 83, trying to get his control down, but he's got nothing to speed the bats up so they sit soft."
Royals: Dyson cleared to play
Center fielder Jarrod Dyson is available if the Royals need him, despite a slightly sprained left ankle.
Dyson spent most of Saturday in the training room and the Royals will be hesitant to use the speedy outfielder as a pinch-runner. Kansas City could also choose to rest Dyson on Sunday because of an off-day on Monday. It all depends on the club's needs.
Dyson injured his ankle on Friday in the eighth inning against the O's, a game the Royals lost, 7-1. Dyson twisted his ankle after sending a liner to center field.
Orioles: Hammel eyes September return
Jason Hammel made a big step in his return from a right knee injury on Saturday when he threw off of an incline for the first time since going on the disabled list on July 15. The starter hopes he can progress enough to return to the rotation by next month.
Hammel is 8-6 with a 3.54 ERA this year, though lingering knee issues eventually required surgery. He's optimistic on his chances to pitch again this season after a strong week of rehab.
"It was moving too slow for me, but in the last three days we've made great strides," Hammel said.
Adam Jones is 6-for-13 (.462) in his career against Chen with one homer and five RBIs. Nick Markakis has also been successful against the lefty, going 6-for-12 with two doubles, two RBIs and two walks.
Royals outfielder Jeff Francoeur is second in the Majors with 12 outfield assists, trailing only Oakland's Josh Reddick (13).
The Orioles unveiled a statue of Hall of Famer Eddie Murray before Saturday's game. It is located behind the bullpens in left-center field.