Smith, a 23-year-old who was acquired from the Angels in 2010, started 10 games earlier in the Minor League season, but switched to the bullpen for his last seven games. He recorded his first professional save last Friday in Omaha's 7-6 victory against Albuquerque.
"It's fun, because I get to come in for one inning and pitch as hard as I can," Smith said. "I miss the routine part of the start and the preparing and all that stuff, so it is still a transition."
Smith -- who was recalled when reliever Kelvin Herrera was optioned to Omaha -- will join Tim Collins and Bruce Chen as lefty options in the 'pen.
"He's been throwing the ball extremely well down there and he's like Timmy, he's more than a situational lefty, guys that can get righties out, too," Royals manager Ned Yost said. "His stuff has jumped up since he's gone to the 'pen, and I'm anxious to see what he can provide."
Smith started one game for the Royals on April 28, allowing seven hits and six runs (four earned) with five strikeouts in four innings in a loss to the Indians. At Omaha, he was 4-3 as a starter with a 3.26 ERA and went 1-0 with a 0.84 ERA in his seven relief appearances, allowing six hits and one run in 10 2/3 innings.
"I'm not saying that long-term he's not going to go back to being a starter, but right now he's going to be a benefit to us out in the 'pen," Yost said.