The Kansas City Royals, coming off their most successful road trip of the season, will return home to face one of the three teams they played on that trip.

The Royals will host the Oakland A's on Friday night in the opener of a three-game series.

Kansas City welcomes back Zack Greinke (0-4, 5.05 ERA) from the 10-day injured list while the A's will send Cole Irvin (2-4, 3.14 ERA) to the mound.

The Royals went 5-4 on their recent trip through San Francisco, Oakland and Anaheim, Calif. They lost two of three to the Giants before taking the series with the A's and Angels. The biggest factor seemed to be strong starting pitching.

In the nine games of the trip, Kansas City starters combined for a 3.42 ERA (18 runs in 47 1/3 innings). They gave up 36 hits and struck out 47. The biggest negative was that only two starters completed six innings.

But manager Mike Matheny believes he sees some of his youthful rotation's promise.

"I believe that we have the makings for that here, too," Matheny said about his staff, referring to the young pitching that carried the Atlanta Braves to 14 division titles from 1991-2005.

"I think that they're pulling for each other, because we're all wearing the same colors. But deep down, they're figuring out that they can make each other better by pushing each other.

Greinke will try to add to that hot streak. He has been out since May 30 with a right flexor strain. It was clear that something was bothering him before he went on the IL.

In his first six starts, he allowed three runs or less and pitched at least five innings. In those starts, he posted an ERA of 2.67, struck out 10 and walked just three. But in his last four starts, he had an ERA of 9.50 with 15 strikeouts, seven walks and five home runs allowed.

He made two minor league rehab starts with Triple-A Omaha. In his second start Saturday, he pitched seven innings and allowed three runs, six hits, including one home run, and one walk. He struck out four.

Matheny said Greinke is fully built up and shouldn't have any limitations.

Greinke is 11-3 with a 2.76 ERA in 24 appearances (19 starts) all-time against the A's.

The A's enter Friday's game on a three-game losing streak. They've won just three of their 19 games in June. They lost to the Mariners 2-1 Thursday, even with Frankie Montas pitching a gem; he had a no-hitter through 7 2/3 innings.

Irvin is 1-1 with a 1.40 ERA in three career starts against Kansas City.

In his last start, he allowed just three hits and one run in 6 1/3 innings against the Royals in Oakland. But he took the loss as the A's were shut out 2-0.

"We haven't been able to put innings or at-bats together over the last four or five games," manager Mark Kotsay said. "Our pitching has been really good on the other end. We've got to score runs to win games. Unfortunately, again, the offense just couldn't get into a rhythm. Couldn't get momentum. Couldn't put hits together."