Chicago (84-68) at Kansas City (69-84)

Even though the Chicago White Sox are atop the AL Central, manager Ozzie Guillen knows they still need to string a few victories together to reach the postseason.

On Friday, the White Sox will face a tough challenge in the opener of a three-game series against the surging Kansas City Royals, winners of seven straight.

Chicago (84-68) kicked off its current 10-game road trip by losing three of four to the New York Yankees including Thursday’s 9-2 defeat.

The White Sox have dropped seven of their last 11 contests, and their division lead was trimmed to just 1 1/2 games over second-place Minnesota, which rallied for an 11-8 win at Tampa Bay. The teams meet for a key three-game set Sept. 23-25 in Minneapolis that will likely decide the division.

With nine regular-season contests remaining, Guillen knows his team needs to start winning again soon.

“We have to keep fighting because nobody said it was going to be easy,” Guillen told the White Sox’s official Web site. “We aren’t playing right now like we are in a pennant race, and if we keep playing like that, it will be tough for us to make the playoffs.”

Chicago’s Javier Vazquez conceded six earned runs in 3 2-3 innings on Thursday as he started on three days’ rest. On Friday, the team will also send Mark Buehrle (13-11, 3.85 ERA) out on short rest, and he is 4-2 with a 3.00 ERA in seven career starts in those situations.

The left-hander has led the White Sox to victory in six of his last eight games - a span in which he is 5-1 with a 3.22 ERA. He turned in a solid outing on Monday, but didn’t factor in the decision after holding the Yankees to two runs and six hits with six strikeouts over six innings of a 4-2 loss.

Buehrle is 6-2 with a 3.55 ERA in his last 12 starts versus Kansas City (69-84), and the White Sox have won 10 of those outings. He tossed six shutout innings, scattering five hits and striking out as many in a 4-0 home victory on Aug. 13 to improve to 18-8 with a 3.45 ERA in 37 lifetime appearances against the Royals.

The Missouri native is also 8-6 with a 3.63 ERA at Kauffman Stadium, where the Royals have won eight of their last 10.

Chicago is 10-5 against Kansas City this season, sweeping a three-game set at home from Aug. 12-14. But the last-place Royals enter on their longest winning streak since reeling off nine in a row from March 31-April 12, 2003.

Kansas City completed a four-game sweep of Seattle with a 12-0 rout on Thursday. Mike Aviles hit a three-run homer, while Alex Gordon and Mitch Maier had two RBIs apiece for the Royals, who are batting .354 during their surge.

“There’s just nothing better than a win,” Royals manager Trey Hillman said. “There’s just no other way to say it.”

To try and continue this tear, Kansas City hands the ball to Brian Bannister (8-15, 4.27), who looks to build off his first win in nearly two months. He was 0-9 with a 7.79 ERA in 13 starts after beating Colorado on June 23, but held Cleveland to three runs and six hits over six innings of a 13-3 victory on Saturday.

The right-hander faced the White Sox three times during his winless stretch, and went 0-1 with a 7.56 ERA. He allowed four runs and four hits, while striking out seven over seven innings in a 9-0 loss in Chicago.

Bannister is 2-2 in eight lifetime starts versus the White Sox.