KANSAS CITY -- The Royals are likely to line up with first baseman Eric Hosmer in right field, designated hitter Billy Butler at first base and right fielder Jeff Francoeur in center this weekend at Pittsburgh.

In Interleague play in National League cities, there's no DH and the pitchers hit.

"We're trying to get our best bats in the lineup. You can't have Billy sitting out," manager Ned Yost said. "We're not sitting Hoz out, he's swinging the bat much better now."

Hosmer and Francoeur have been working out at their new positions for the past three weeks and Butler is constantly practicing at first base.

"When you're a lefty in Little League and a pretty big kid, there's not many positions you can play, so I've been stuck at first base for a while and it'll be fun for me to be out there," Hosmer said.

Hosmer played the outfield briefly in two Spring Training games, but has not played there in the Minor Leagues or the Majors. He last played outfield regularly in summer ball as a high school senior. Francoeur has played center field in the Majors just twice, both times in 2006 for the Braves. Butler has logged 333 big league games at first base.

"We went into it last year with Billy on the bench, but the way Billy's swinging the bat this year we can't afford to do that," Yost said. "We've got to have Billy on the field during these National League games."

If Hosmer and Francoeur converge on a fly ball in the right-center-field gap, Hosmer knows who'll be in charge.

"Frenchy," Hosmer said. "Any ball he can get, he's going to go ahead and take care of that. If I'm out there, I'll just handle the line and anything he can't get to out there."

With speedy center fielder Jarrod Dyson out of the starting lineup, the defense is likely to suffer.

"Some," Yost said. "But we'll switch out in the seventh inning or so, depending on the situations. We'll have all our pinch-hit priorities set and our defensive switches set."

Catcher Perez assigned to Triple-A Omaha

KANSAS CITY -- Catcher Salvador Perez has been assigned to Triple-A Omaha to continue his road back from left knee surgery.

Perez will report to the Storm Chasers on an injury rehabilitation assignment for their Thursday night game against Round Rock.

"We want to get him back to playing nine innings," manager Ned Yost said. "He caught seven innings yesterday [in Arizona extended camp] with four at-bats. We don't know how long it'll be. It won't be another month, I can tell you that."

When Perez underwent surgery on March 16, he was expected to be out until the All-Star break. But even if he spends his entire 20-day rehab allotment with Omaha, he'd return by June 27.

"He's not going to be an everyday player when he first gets here, because we've got to work him back into that everyday routine," Yost said. "But I imagine he can catch four days a week when he first gets here and we're trying to prepare him for that schedule."

Perez, who has been in Arizona since May 20, has not yet caught on back-to-back days, according to Yost.

He'll be joined in rehab by second baseman Chris Getz (bruised rib cage) and pitcher Everett Teaford (abdominal strain) at Omaha on Thursday. Pitcher Jonathan Sanchez (biceps tendinitis) is already there, awaiting his third start. Yet to be assigned are catcher Manny Pina (knee surgery) and center fielder Lorenzo Cain (hip flexor strain).

Starling to begin play June 19

KANSAS CITY -- Now that the 2012 First-Year Player Draft is over, the Royals' top choice in 2011 is finally ready to join a team.

Outfielder Bubba Starling is expected to begin play on June 19 with the Rookie classification team at Burlington, N.C., a member of the Appalachian League. Starling signed too late last summer to be assigned to a regular-season team.

"We're happy with [Starling's progress]," said J.J. Picollo, assistant general manager-scouting and player development. "This whole process from Spring Training to now is just to build a foundation for Bubba. Being on the field every day, being in warm weather every day, taking batting practice on the field every day, being around [hitting coach] Andre David and a lot of the people that we hold in high regard has helped his progress as a player.

"We think what we're going to see with Bubba is things are going to start speeding up as far as his development in the coming year to 18 months. It's building a foundation for him. He's done a great job with it."