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09/18/11 1:39 PM ET

Stewart riding roller-coaster season

KANSAS CITY -- Chicago pitcher Zach Stewart dropped to 2-5 after taking the loss in the White Sox's 10-3 loss to the Royals last night.

It was Stewart's 10th career start and second against the Royals. After giving up five runs and 11 hits to Kansas City, Stewart has now allowed seven earned runs in 11 1/3 innings against the Royals.

In his last outing, he gave up three runs in five innings to Cleveland, but on Sept. 5, he threw a one-hit shutout against Minnesota with nine strikeouts. Stewart has been up and down a bit through his starts, but doesn't have any good explanation as to why.

"I try to be as even keel as possible every start," he said. "I guess the way these starts have played out, it looks that way [uneven]. I don't feel like I'm doing anything to initiate that or make it that way, it's just been that way."

The 24-year-old said he's glad to be up in the Majors and getting experience, but expects to compete.

"At the same time, I don't want to just go out and go through the motions just because I'm here," Stewart said. "I'm still trying to get better to where I can stay at this level or compete instead of having outings like this."

Ozzie impressed with KC's Perez

KANSAS CITY -- White Sox manager Ozzie Guillen had some kind words for Royals catcher Salvador Perez, a fellow Venezuelan.

"This kid ... I hope he continues to play the way he [does]," Guillen said. "Because after three years in the big leagues, you don't have the enthusiasm, the fight. This kid, behind the plate is outstanding, and he's a better hitter than what people think. I think this kid's got a bright future."

The rookie has a pickoff and caught Alejandro De Aza stealing in the series.

He's also 6-for-12 in the series entering Sunday, with two runs, a double, a triple, an RBI and two walks, as part of a young Royals lineup that has hit the White Sox pitchers hard.

"He will help the ballclub, because he has all the tools to do it," Guillen said

Adam Holt is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.