Chicago ? After a 4-2 loss to the Chicago White Sox on Wednesday night, Kansas City Royals manager Tony Pena screamed at his players behind closed doors in the clubhouse.

A.J. Pierzynski hit a two-run homer to help the White Sox to their fourth straight victory overall and fifth in a row over the Royals.

While Chicago improved the best record in the major leagues to 20-7, the last-place Royals lost for the 14th time in 17 games and dropped to 7-20 despite outhitting the White Sox 9-6.

“I’m not happy,” said Pena, whose yelling could be heard from outside the clubhouse. “It’s not the effort. They give me effort. I just see something that I don’t like.”

Chicago increased its AL Central lead to 41/2 games over second-place Minnesota and is 17-4 in the division.

“I expect us to do even better,” said Dustin Hermanson, who earned his fourth save with 12/3 innings of relief. “This a good team here. It’s a long season to go. It is a marathon. But this isn’t a fluke.”

Former Royal Jermaine Dye’s RBI single broke a 1-all tie in the fourth, and Pierzynski followed with his second homer of the season. Aaron Rowand started the rally with a two-out bloop single and scored on Dye’s hit.

“We’re coming up with big hits in timely fashion, and our pitchers are doing a heck of a job keeping us in the ball game,” Dye said.

Freddy Garcia (3-1) gave up two runs and eight hits in 61/3 innings, and Hermanson, Chicago’s fifth pitcher, got five straight outs.

“Freddy threw the ball better today,” White Sox manager Ozzie Guillen said. “He came out and threw strikes, and his fastball looked pretty good today.”

Hermanson came in with one runner on in the eighth and got a flyout and strikeout to end the inning, then retired the side in the ninth on two groundouts and a popout. Hermanson has not allowed a run in 13 innings over 11 appearances this season.

“We’re not scoring that many runs right now,” Guillen said. “If we don’t play good defense, we’re in trouble.”

Runelvys Hernandez (1-4) lost his fourth straight decision, giving up four runs and six hits in 71/3 innings. All but one of the batters who reached on the first five hits Hernandez allowed, scored.

“Today was one of my best games and nothing, you know,” Hernandez said.

“He pitched well,” Pena said. “The one bad inning was it.”

Garcia was in jams all game, and his bullpen inherited one in the seventh. Garcia was pulled with one out and two on.

After a passed ball advanced the runners to second and third, Neal Cotts loaded the bases with a walk to Ruben Gotay. Cliff Politte came in and gave up Mike Sweeney’s sacrifice fly to center, with Mark Teahen sliding to just beat the throw from Rowand on a close play. Politte then struck out Ken Harvey to end the inning.