It surfaced Tuesday, as Meche gave up five runs on seven hits and walked five against the Blue Jays in his shortest outing of the season.
"I think he's going to be OK," said Hillman, who, citing club policy, couldn't go into detail about Meche's medical tests. "[He's] just a little stiff in the right low back."
For now, the Royals are taking a patient approach with Meche's ailment, but Hillman said he hopes it doesn't turn into a situation where the Royals have to wait until Meche makes a start to see if he'll experience discomfort.
"It's just like [Tuesday], we didn't know there was an issue until we actually took him out," Hillman said. "He's going to keep taking the ball if he feels he can go out there."
And that's exactly where the Royals need him. Losing Meche for any significant amount of time would be devastating for a team that has featured one of the best rotations in the Majors.
Entering Wednesday, Kansas City's starters had a 3.47 ERA -- the second-best ERA for a rotation in the big leagues behind the Cardinals, whose starters have posted a 3.14 ERA.
Meche, who was 14-11 with a 3.98 ERA in 2008, was sharp in his first four outings. He entered his start Tuesday with a 2.63 ERA in four starts. And before allowing five walks on Tuesday, he had 25 strikeouts compared with just four walks.
But command was a major problem in the loss to the Blue Jays, which dropped Meche's season totals to 1-2 with a 3.77 ERA.
"You always kind of wonder when you see that kind of lack of command with Gil, but he had a great action to his curveball, he still had good velocity," Hillman said.
"He looked liked he was finishing his pitches, but then when you [saw] it from the different angle than we had in the dugout, he was going east to west a lot on release."
The results weren't good, and the sight of watching Meche walk off with a trainer at his side was even worse.
Meche said after the game that he expected to pitch Sunday, and Hillman said nothing to refute Meche's words.
"He doesn't want to give the ball up," Hillman said. "He wants to pitch."