Oakland (93-69) at Kansas City (62-100)

Already concerned with injuries to two of their top pitchers, the Oakland Athletics would feel some relief by getting a solid, pain-free outing from Esteban Loaiza.

The 12-year veteran hopes to lead the Athletics to their 12th consecutive victory at Kauffman Stadium as they face the major league-worst Kansas City Royals on Saturday.

Oakland would benefit from Loaiza staying healthy after having to place right-hander Rich Harden on the disabled list Friday due to a strained back muscle. Leading the team’s starters with a 3-0 record and 4.06 ERA, Harden is expected to be sidelined three to six weeks.

“We’re undefeated when he pitches” this year, A’s manager Macha said, “so this is pretty significant.”

Another injury problem for Macha involves Huston Street, who may soon return from a pectoral muscle injury that has sidelined the team’s closer since April 18.

Loaiza (0-3, 8.35 ERA) is making his first start since Sunday, when he was removed after 3 2-3 innings due to back spasms in a 4-3 loss to the Los Angeles Angels. Loaiza, who gave up three runs and seven hits, had felt tightness in his back while stretching before the game and had a similar problem in spring training.

“In spring it went away,” said Loaiza, who threw 45 pitches off a mound on Tuesday in a rehab session. “It’s not a good feeling for me. I want to pitch seven innings.”

Loaiza has the highest ERA in the team’s starting rotation, is allowing hitters a .385 batting average and has only reached the sixth inning once in four starts.

The right-hander signed a three-year, $21.4 million contract with the A’s in the offseason after spending 2005 with the Washington Nationals.

He has won his last three starts against the Royals—as a member of the Chicago White Sox—but last faced them on April 13, 2004.

Kansas City’s Mike Sweeney, who homered Friday for the first time since April 8, is 10-for-26 (.385) with three home runs and seven RBIs against Loaiza.

The Athletics (11-12) won their 11th in a row at Kansas City with a 5-3 victory in the opener of this three-game series on Friday.

Mark Ellis homered and tied a career high with four RBIs as Oakland won for the 17th time in its last 18 games at Kauffman Stadium. The A’s haven’t lost a series there since July 1999.

The Royals (5-16) will start Jeremy Affeldt (1-2, 6.27), who is trying to build on his first win of the season.

The left-hander gave up one run and had six strikeouts in 5 1-3 innings of a 5-1 win over Cleveland on Sunday. He is one of two starters on the staff to record a victory.

“I’m working a little bit quicker,” said Affeldt. “I worked pretty quick the first two games, but when you throw a lot of balls it seems you work slower. I changed that and I’m throwing more strikes.”

Kansas City is still without closer Mike MacDougal, who is sidelined with a strain below his right shoulder, suffered during spring training.

The right-hander may not return until June and Ambiorix Burgos, who has two saves in three chances, will continue to fill the void.

“Burgos has done pretty good, but this has our bullpen out of sync,” Royals manager Buddy Bell said. “It puts everybody in different roles, whatever those are.”