German would be his choice over Mark Teahen, who played right field last year, or Joey Gathright, who has had a terrific Spring Training.
Guillen faces a 15-day suspension at the start of the season. It's under appeal, but, if not lifted, he'd miss the Royals' first 12 games.
"I would probably lean toward going with German, who's played very well out there, and leaving Teahen alone in left," Hillman said.
Hillman indicated he'd prefer to leave Teahen in left field, where he's played this spring, and not try Gathright in right, where he's not played during camp.
"It's a possibility. He's had a great spring," Hillman said. "But the importance of getting the most out of any player is making sure that they're comfortable with the position they're playing."
German has a stronger arm, essential in right field, than Gathright, Hillman noted.
"And defense is right behind pitching for me in performance, and we've done a real good job with our cuts and relays. Joey's thrown the ball better than I anticipated, but it still doesn't play out as strong as German's does," Hillman said.
Hillman has been impressed with German's play in right field. Going into Tuesday night's game against the Padres, Gathright was out-hitting German, .354 to .217.
In fact, Gathright has been one of Hillman's biggest highlights in Arizona.
"He's playing with a lack of fear that his tools promote him to be very productive with," Hillman said. "If he's fearful on the basepaths or fearful in the outfield going after balls and getting reads and jumps, his tool in speed is not going to play out. [But] it's played out consistently all of Spring Training."
Hillman said that Gathright, who has played in center and left, has made "false steps" in the outfield.
"But he's made up for it with his speed. On the basepaths he's been outstanding, his bunting game has been exceptional and he's just playing with a lack of fear, so he's been very good for me," he said.
Teahen went through a change from third base to right field last season, and Hillman doesn't want to disrupt him again. Teahen already is being primed for some duty at first base, where he started Tuesday night's game.
German played left field against the Padres and missed a fly ball for an error in the second inning. On the next play, he couldn't run down a long drive near the wall.
The Royals have not heard from the Commissioner's office on Guillen's appeal, or on catcher Miguel Olivo's appeal of a five-game suspension.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.