KANSAS CITY -- Closer Joakim Soria will begin a rehab assignment in Arizona on Wednesday, Royals manager Trey Hillman said before Monday's series opener against Detroit.

Soria threw another 25-pitch bullpen session on Monday, and on Tuesday, he'll travel to Arizona, where he'll throw in two extended spring training games.

Soria said his injured right shoulder felt good, and that he was throwing as hard as he would in a normal bullpen session.

"It's not the same as a game," said Soria, who was placed on the 15-day disabled list on May 10 with a right rotator cuff strain. "It's not the same situation. You have to do more in a game."

Soria will get the opportunity to pitch in a game in Arizona. Hillman said he'd throw 15 pitches on Wednesday, take two days off, and then throw 25 pitches on Saturday.

"If everything goes as planned, [he'll] possibly fly back here either Saturday evening or Sunday and we'll see where we're at," Hillman said.

Soria has been battling a sore shoulder all season. He's seven-for-seven in save opportunities, but the injury has limited his availability and performance.

Soria has pitched just 8 2/3 innings in eight appearances. He last pitched in a game on May 7, when he allowed one run in a save against Seattle.

But Hillman said Soria's rehab has gone well.

"It's been encouraging," Hillman said. "He hasn't moved backwards and he continues to move forward."

Soria, who had a breakout season in 2008 with 42 saves and an All-Star Game appearance, said he threw all his pitches during his bullpen session, and he's ready to get to Arizona.

"I have to do everything that I have to do and try to get back soon," Soria said.