Boston (66-50) at Chicago (64-51)

Chicago White Sox manager Ozzie Guillen felt confident last week that Jose Contreras would come off the disabled list a completely different pitcher than the one that struggled in June and July.

Contreras tries to live up to his manager’s expectations when he takes the mound Saturday night as the White Sox and Boston Red Sox continue a four-game series.

This will be the first start since July 13 for Contreras (7-6, 4.60 ERA), who was placed on the disabled list July 20 with elbow tendinitis after going 1-3 with an 8.60 ERA over his last seven starts.

Prior to those struggles, the 36-year-old right-hander had been pitching well, going 6-3 with a 2.76 ERA over his first 12 starts this season. Guillen told the White Sox’s official Web site last week that he expects to see more of that Contreras now that he’s healthy.

Contreras is 3-4 with an 8.43 ERA in nine career starts against the Red Sox, including 1-0 with a 4.63 ERA in two starts against them in Chicago.

“If Contreras throws the way (pitching coach Don) Cooper says,” Guillen said, “he’s not going to lose another game this year. See you later, Minnesota Twins - guaranteed.”

The White Sox (64-50) maintained a half-game lead over the Twins in the AL Central with a 5-3 victory in Friday’s series opener. Mark Buehrle pitched seven strong innings, allowing one run and four hits, while Orlando Cabrera drove in two runs to help Chicago win for the third time in four games.

The Red Sox cut Chicago’s lead to 4-3 in the eighth after Dustin Pedroia hit a three-run homer, but Carlos Quentin responded in the bottom of the inning with a solo shot - his league-leading 31st.

Boston’s lead over the Twins in the AL wild-card race was sliced to 1 1/2 games. The Red Sox (66-50), who had won 15 of their previous 20 games in Chicago, dropped 3 1/2 games behind AL East-leading Tampa Bay. They had five hits on Friday after scoring eight runs in each of their previous two wins against Kansas City.

“(Buehrle) pretty much shut us down,” Pedroia told the Red Sox’s official Web site. “We had nothing going.”

Daisuke Matsuzaka (12-2, 3.04) takes the mound Saturday for Boston.

Matsuzaka pitched six innings against Oakland on Sunday, allowing two runs and four hits in a 5-2 win. He had allowed six runs in five innings of a 7-5 loss to the Los Angeles Angels in his previous start.

“He wasn’t as bad as his line last time,” catcher Jason Varitek said. “He’s better his last four, five starts than he was his first eight, nine when he didn’t have a loss.”

The right-hander has won three of his last four starts and the Red Sox are 15-4 this season with Matsuzaka on the mound.

He allowed three runs and two hits while walking six over five innings of a 4-2 loss on July 19, 2007 in his only career appearance against the White Sox. Matsuzaka is 5-0 with a 2.20 ERA in eight road starts this year.

Boston hasn’t lost twice to the White Sox in the same series since 2005, when the teams split a four-game series in Chicago.