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6/3/2014 1:43 A.M. ET

Chen set for rehab start; Ventura ready to return

ST. LOUIS -- Royals left-hander Bruce Chen is set to begin his Minor League injury rehabilitation assignment Tuesday night.

Chen is scheduled to pitch for Double-A Northwest Arkansas at Springdale, Ark., against Tulsa.

He's been out since April 25 with a bulging disk in his back. He had made four starts with a 1-2 record and a 7.45 ERA. His spot in the rotation was taken by lefty Danny Duffy, who pitched six innings in Monday night's 6-0 victory over the Cardinals.

On Monday afternoon, right-hander Yordano Ventura threw a successful side session, and he is ready to start Thursday night against the Cardinals in Kansas City.

Ventura skipped his last start after being pulled out of a Memorial Day game against the Astros in the third inning because of concerns over his elbow. He's since been cleared to resume pitching.

Royals promote Rodriguez, option Coleman

ST. LOUIS -- Wilking Rodriguez has replaced Louis Coleman in the Royals' bullpen as the club swapped out right-handed pitchers Monday.

Rodriguez was brought up from Triple-A Omaha and Coleman was optioned to the Pacific Coast League club.

To make room on the 40-man roster for Rodriguez, left-handed pitcher Justin Marks was designated for assignment.

Rodriguez, 24, was signed as a Minor League free agent last winter after seven seasons in the Tampa Bay organization. He began the season with Double-A Northwest Arkansas, giving up two earned runs and 11 hits in 11 innings with 12 strikeouts and four walks. Promoted to Omaha, he'd made just two one-inning scoreless outings last Tuesday and Wednesday.

"He's a kid that has a power arm. He's 95 to 100 miles an hour, good breaking ball. He's had some issues with his shoulder, but he's completely healthy now," manager Ned Yost said. "We'll take a look at him. He's throwing the ball good now."

A Venezuela native, Rodriguez had shoulder surgery in October 2010. In his eight seasons in the Minors, he has a 10-27 record and a 3.80 ERA in 101 games (64 starts). This is the first year that he's played above the Class A level.

Coleman pitched 17 times in relief for the Royals and had a 1-0 record, a 6.27 ERA and opponents were hitting .316 against him.

"Louie Coleman is a real important part of our 'pen," Yost said. "He's a guy we look to match up with [Kelvin] Herrera, [Aaron] Crow, [Tim] Collins -- we need all four of those guys to be producing and Louie just wasn't. He kind of got relegated to a mop-up role and we can't have that. He's too good for that. So we wanted to send him down and get his slider going again and get him to command his fastball again and go from there."

Coleman had a setback early in Spring Training when the middle finger of his pitching hand was struck by a ball. It was sore and swollen and he began the season on the disabled list, rejoining the club April 9.

"He just hasn't gotten going yet," Yost said. "The thought is to get him down there, get him pitching more consistently. He did it last year. He wasn't real sharp. We sent him down and when he came back, he was lights-out, really. The hope is we can do it again -- get him down there, get him back quick."

Marks had a 3-2 record and a 5.64 ERA in 13 games (two starts) for Omaha.

Butler moves to pinch role for two-game set

ST. LOUIS -- Eric Hosmer will play first base and Billy Butler will be a pinch-hitter off the bench in the two-game Interleague series at Busch Stadium.

The Royals lose the designated hitter in National League cities when the pitcher bats. Butler is the DH but also has played first base in the past.

No surprise that the left-handed-hitting Hosmer was in the lineup against right-hander Shelby Miller on Monday night. But Butler will be on the bench again Tuesday night, even though the Cardinals are starting a left-handed pitcher, Jaime Garcia.

"I'm going to play Hoz," Yost said. "You've got a Gold Glove first baseman there and Hoz is swinging the way Billy's swinging, so I'm not going to lose the defense for the same amount of offense."

Going into the series opener, Hosmer was hitting .271 with one homer, 23 RBIs. Butler was at .249 with one homer, 21 RBIs.

Royals get reliever Wood back on waivers

ST. LOUIS -- Right-handed pitcher Blake Wood, originally selected by the Royals in the third round of the 2006 First-Year Player Draft, has returned to the organization.

Wood, 28, was claimed off waivers from the Cleveland Indians and assigned to Triple-A Omaha, the Royals announced Monday. To make room on the 40-man roster, pitcher Luke Hochevar was placed on the 60-day disabled list. Hochevar is out for the season after elbow surgery.

Wood pitched in 106 games for the Royals in the 2010-11 seasons with a combined record of 6-6, one save and a 4.30 ERA.

"He came up and, at times, pitched really well," manager Ned Yost said. "He had a good, heavy two-seamer, really good action. Not a very good secondary pitch, not very good at holding runners but had a power arm."

But in 2012, he underwent Tommy John surgery, the same year that Joakim Soria, Danny Duffy and Felipe Paulino also had the elbow procedure.

"He had the Tommy John and now he's got his power arm back. It's just getting back to refining his command to where he can be productive with his power arm," Yost said.

"He came back last spring with Cleveland and looked good. He looked even better this spring when we saw him."

Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.