KANSAS CITY -- Those that know Brian Bannister know he is an analytical guy.

He studies stats. He looks at trends. Simply put, Bannister explores the game of baseball.

So the easy answer is, yes, Bannister has looked at his extreme day-night splits.

He's seen the numbers -- a 15-6 career record with a 4.31 ERA during the day, and a 13-26 record with a 4.83 ERA at night.

And Bannister thinks he has the answer. It's nothing more than one of those curious baseball oddities, he says.

"I have the exact same opponent batting average and my ERA is almost identical [in day and night games]," Bannister said. "So the answer to that is my team scores more runs for me during the day."

That certainly seems plausible. Opponents are hitting .264 against him during the day compared with .270 at night. Opponents' on-base and slugging percentages are similar as well.

But here's the thing. In his third full season in the Majors, Bannister's splits are even more extreme.

This year he's 3-2 with a 2.38 ERA during the day and 2-4 with a 4.97 ERA at night.

At the very least, consider it a positive that Bannister will take the mound on Sunday afternoon against the White Sox in the final game of a four-game series.

So that's the good news. The bad news is that Bannister -- with a 2-4 record and an 8.15 ERA -- doesn't exactly have a sterling track record against the White Sox.

"The core of their team is the middle of their lineup," Bannister said. "It's stayed the same for the past couple years and they're extremely dangerous.

"You have [Jim] Thome, who is going to be in the Hall of Fame, and Jermaine Dye, who is an annual All-Star, and that's just a tough middle of the order to get through."

And while the White Sox have surged in the past few weeks, the Royals' offense has plummeted. However, help could be on the way.

Catcher John Buck concluded a rehab assignment with Triple-A Omaha on Friday, and Royals manager Trey Hillman said Buck would probably travel back to Kansas City on Saturday.

"He won't be on the roster [Saturday]," Hillman said. "We'll look at our roster options, and make a decision on what we're going to do."

Buck hasn't played since May 30, when he exited a game against the White Sox with a herniated disk in his back.

Meanwhile, Bannister would just like to continue what has been a strong comeback season in 2009.

After going 12-9 with a 3.87 ERA in 2007, Bannister regressed with a 5.76 ERA and a 9-16 mark in 2008.

He started the season with Omaha before making his 2009 debut with the Royals on April 22 at Cleveland.

When he got back to the Majors, Bannister had a plan. First, he ditched his four-seam fastball -- a pitch he calls an "extreme fly-ball pitch" -- for a two-seam cut fastball. Secondly, he wanted to lower his walks and improve his strikeout and ground-ball ratios.

"My goal has been to get back to the win-loss record and the ERA that I posted in 2007," Bannister said. "But with the peripherals to support it -- with the walks, the strikeouts, the ground balls and the home runs that really support that number.

"For the most part, I've been able to do it. It took me a year to get back there. But I've been able to do it, and I feel like I'm continuing to mature as a pitcher at this level."

Pitching matchup
KC: RHP Brian Bannister (5-6, 3.93 ERA)
Bannister was very sharp against the Twins last Tuesday night, but he lost, 2-1, because of one home run and one unearned run. He worked seven innings, allowing six hits and one walk with six strikeouts. Of the other 15 outs, six were groundouts, which indicates that Bannister, a fly-ball pitcher, was getting a good share of balls hit on the ground. He's given up just nine earned runs in 34 innings over his past five starts for an ERA of 2.12. The White Sox gave Bannister one of his toughest times all season, burning him for seven runs on 10 hits on May 29.

CWS: LHP Clayton Richard (3-1, 4.48 ERA)
After struggling in his two previous starts, Richard had a positive outing against the Indians on Tuesday. Although he gave up four runs in six innings, three of those runs came after he returned from a 30-minute rain delay. He earned his first complete game when the game was called in the top of the seventh inning because of rain. Richard pitched six innings and gave up four runs on four hits while striking out six and walking one. In his most recent start against the Royals on May 29, Richard pitched seven innings and gave up just two runs. The left-hander is 1-1 with a 4.15 ERA in five appearances -- two starts -- against the Royals in his career.

Crown Points
Injured right-handed reliever Doug Waechter, who started the season with the Royals, began a rehab assignment on Saturday with Triple-A Omaha. Waechter has been out since April 18 with an elbow injury and strained oblique. ... The Royals have signed another 16-year-old international prospect, Luis Villegas of Venezuela. Villegas is a 5-foot-10, 170-pound catcher. ... Judge Jay Daugherty sat in the Buck O'Neil Legacy seat on Saturday. Daugherty is a long-time advocate and volunteer for the local chapter of the ALS Association. Since 1985, Daugherty has been on the board of directors for the chapter while also serving as a trustee on the national board for more than 10 years. ... The first 10,000 kids 14-and-under will receive G-Force trading cards on Sunday.

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Up next
• Monday: Royals (Gil Meche, 4-8, 4.20) at Tigers (Armando Galarraga, 5-7, 5.34), 6:05 p.m. CT
• Tuesday: Royals (Bruce Chen, 0-2, 4.38) at Tigers (Justin Verlander, 8-4, 3.54), 6:05 p.m. CT
• Wednesday: Royals (Zack Greinke, 10-4, 2.00) at Tigers (TBD), 6:05 p.m. CT