KANSAS CITY -- Left-hander John Bale is doing so well in his injury rehabilitation assignment that he's moving up to Triple-A Omaha.

"I've been promoted," he said with a smile.

Bale stopped by the Royals' clubhouse Wednesday night on his way to Omaha from pitching in six games with Double-A Northwest Arkansas. He had a 1.35 ERA, giving up one run, four hits and one walk with five strikeouts in 6 2/3 innings.

Bale said plans are to pitch four or five times for Omaha, then possibly return to the Royals when his 30-day rehab assignment is up on June 3.

"The velocity is coming up, and with the adrenaline coming back here, it should shoot up even more. With more people in the stands, it'll naturally go up. At least it did last year," he said.

Bale estimated that, including his stay at extended spring training in Arizona, he's thrown 27 innings.

Counted on as a left-hander in the bullpen this spring, he was sidetracked at the Surprise camp by thyroid surgery. Since losing a considerable amount of weight due to the thyroid problem, he's back up to his normal 220 pounds.

"His velocity readings are between 86 and 89 [mph] and the ball's getting out of his hand good," manager Trey Hillman said. "He's spinning the ball good and he doesn't have any physical issues."

Bale finished his Northwest Arkansas stay on Tuesday when he threw one perfect inning in a 10-0 victory over Tulsa, throwing 21 pitches -- including 16 for strikes.

Hillman said Bale's emphasis now is adding endurance.

"If we ran into an emergency situation and had to [bring him up], I think we could force the issue, but we'd rather see a longer period of time [in rehab] and have him build his stamina," Hillman said.

Closer Joakim Soria played catch for the second consecutive day with no setbacks. There remains no definitive timetable for his return.

"I think he's still three to five days away from where he can even consider getting up on the mound," Hillman said.