CHICAGO -- It's been a rough stretch for cerebral Royals starter Brian Bannister. First, he missed about five weeks of big league time with tendinitis in his pitching shoulder. Then, when he returned to the Majors on Tuesday, the Twins knocked Bannister around to the tune of seven runs and eight hits over 2 2/3 innings.

It'll likely be his last start for awhile.

"Bruce [Chen] has been pitching so well and did it again last night," said Royals manager Ned Yost. "I thought long and hard about putting Bruce in the 'pen, but I'm probably going to put Banny in the 'pen for the next couple of weeks and use him like in a Gil Meche mode."

Chen threw seven strong innings against the White Sox in a 4-3 loss on Friday. Yost said Bannister is well enough physically to keep pitching.

"He feels good and his shoulder is strong, but we're trying to win ballgames up here, too," said Yost. "Bruce has put together some real good ballgames for us lately and he's making strides, and I just don't feel like taking him out of the rotation."

Yost added that the organization is committed to an extended evaluation of starter Sean O'Sullivan, who was acquired from the Angels in July. Also, Kyle Davies has been throwing well lately, and Yost isn't about to yank American League Cy Young Award winner Zack Greinke or Luke Hochevar from the rotation.

"Those two are a big part of what we're trying to do here," Yost said.

Catcher Pena getting more experience

CHICAGO -- This is a month of mixing evaluation with trying to win games for the Royals. Among the players getting an extended look is catcher Brayan Pena, who was seldom seen before durable starter Jason Kendall went down with a torn rotator cuff.

Pena has been almost exclusively a catcher at the big league level, but he did spend time at first base, third base and the corner outfield positions in the Minors. While that adds to his versatility, he remains relatively inexperienced behind the plate. However, he's worked closely with Royals bench coach John Gibbons and appears to be making strides.

"This is his first opportunity to do anything," said Gibbons. "He's kind of been that guy that hasn't had a position. He's very valuable because he can play other positions.

"He's still basically learning the position. It's not easy, but I think he's done a tremendous job throwing the ball and I think he has very good hands. The finer points [come] the more he's back there."

Based on his Minor League stats, Pena's bat will play extremely well as the backup catcher if the team can trust his defense. His offense in the Majors has been sporadic, but has been solid over the last month and he's becoming more consistent the more he gets on the field.

"The amount of games that Jason catches, there really isn't much chance for [Pena] to get on the field," said Gibbons. "In limited playing time, it doesn't matter how good of a hitter you are, you're not going to have your timing. The more he plays ... that's one thing he's always been able to do, is hit."

Pena was hitting .245 with 12 RBIs entering Saturday's game against the White Sox, and has drawn 11 walks in 117 plate appearances. He's thrown out nine of 26 (.346) opposing basestealers this season.

Ka'aihue to play more against lefties

CHICAGO -- There were a lot of Royals fans clamoring for first baseman Kila Ka'aihue, who has torn up pitchers at Triple-A Omaha over the past three seasons. Ka'aihue has now been playing in the Majors regularly for about five weeks after being recalled in early August.

"It's been a bit of struggle for him offensively," said Royals manager Ned Yost. "He's done a real nice job for us defensively. It's just [a matter of] getting settled in the big leagues a little bit.

"It's an adjustment coming up, because the talent is so much better and the pitchers are so much more consistent."

In terms of results, Ka'aihue appears to still be settling in. Entering Saturday's game, Ka'aihue was hitting .190 with three homers and 10 RBIs in 105 at-bats. He reached the Majors with a reputation as a hitter with a patient approach, and his 11 walks indicate that part of his game has translated from the Minors.

"I feel good," said Ka'aihue. "[I've had to adjust] my day-to-day approach in the [batter's] box. In Omaha, it seemed like everybody was a little bit similar. Here, everybody is different. "

At Omaha, the lefty-hitting Ka'aihue really didn't display a dramatic platoon split. However, he's just 4-for-31 (.129) against southpaws at the big league level this season and has sat against lefties this week with the Royals going against playoff contenders. Yost said Ka'aihue will get more work against lefties before the season is over.

"It's just about getting your feet on the ground," said Yost. "His success against lefties has been less than limited. Next week, he'll play against lefties. In these games [against Minnesota and Chicago], I had to put the guys in who I thought gave us the best opportunity to win these games."

Yost's son is a NASCAR graduate

CHICAGO -- Royals manager Ned Yost was a late arrival for Friday's game as he flew into Chicago from North Carolina after attending graduation of his son, Andrew, from the NASCAR Technological Institute. The ceremony was held in Mooresville, N.C., which is about 30 miles from Charlotte.

"He's real excited about it. He's worked hard," said Yost. "He's gone to school up there for a year and half and has done really, really well."

Yost, a noted NASCAR fanatic, was a close friend of late racing legend Dale Earnhardt Sr. and remains close with Dale Jr. and the rest of the family. Despite the connections, Yost said his son isn't planning to join a NASCAR pit crew, but is instead headed toward becoming a master mechanic.

Worth noting

Royals were 1-6 at U.S. Cellular Field after dropping Friday's game, 4-3. Overall, the teams have played nine games decided by two runs or fewer. The Royals are 4-5 in those games. ... The Royals are 26-29 in one-run decisions this season. The 55 one-run games is the most in the Majors. ... Double-A Northwest Arkansas evened its Texas League division series against Springfield with a 5-2 win on Friday. Naturals starter Everett Teaford threw seven shutout innings to pick up the win. ... Billy Butler was in the lineup again on Saturday for the second consecutive night. He missed Wednesday's game in Minnesota with a bruise on his right hand.