BOSTON – Infielder Kevin Youkilis, the first Boston Red Sox prospect to play for the Portland Sea Dogs and a Fenway Park favorite for his production and all-out play, has been traded to the Chicago White Sox.

Youkilis, 33, was dealt Sunday to the Chicago White Sox for right-handed pitcher Zach Stewart and utility player Brent Lillibridge. The Red Sox, according to published reports, will pay about $5 million of the remaining $7 million on Youkilis’ contract.

Stewart, 25, will report to Triple-A Pawtucket, while Lillibridge will replace Youkilis on the major league roster.

“We talked to several teams and this seemed like the right fit,” Boston General Manager Ben Cherington said of what Boston got in the trade. “It was a combination of talent and savings.”

To make room for both players on Boston’s 40-man roster, Sea Dogs outfielder Oscar Tejeda was designated for assignment. He could be picked up by another team, traded or reassigned to the minor leagues once he clears waivers.

The trade for Youkilis came as no surprise, since he lost his starting job to rookie third baseman Will Middlebrooks, who starred at Hadlock Field last year.

“This wasn’t something that was out of the blue,” said Red Sox outfielder Cody Ross. “Everyone kind of saw it coming, even him.”

Youkilis was not available for comment. He left the game in the seventh inning after he tripled and was removed for pinch runner Nick Punto.

It became obvious that something was up the way Youkilis was hugged by Punto in the infield, and then by his other teammates in the dugout.

Youkilis received a standing ovation and more cheers when he came out for a curtain call, urged by Manager Bobby Valentine and his teammates.”

“No one has earned that more than him,” Middlebrooks said.

Middlebrooks, 23, is the reason for Youkilis’ departure. He was called up on May 2 when Youkilis went on the disabled list because of a sore back.

Middlebrooks has been stellar in 41 games, batting .326 with nine home runs and 34 RBI.

“With the way Middlebrooks has been playing, he needs to be in the lineup,” Cherington said. “That’s pretty clear.”

Middlebrooks shined in Portland last year, bating .302 with 18 home runs before a late-season promotion to Triple-A. But no one saw him developing this quickly into a major-league regular.

“It’s fair to say we thought this would be his year in Triple-A,” Cherington said. “Things change. Sometimes opportunities open up and guys just speed the clock up. This was a combination of both.”

Youkilis, meanwhile, has struggled, batting .233 with four home runs and 14 RBI in 42 games.

Youkilis, an eighth-round draft pick out of the University of Cincinnati in 2001, began the 2003 season with the Portland Sea Dogs, the first year of Portland’s affiliation with the Red Sox. He batted .327 in 94 games.

First promoted to the majors in 2004, Youkilis came into this season with a .289 career average, 129 home runs and 550 RBI. He was one of only two remaining Red Sox with World Series rings from both 2004 and 2007, along with David Ortiz.

“He did a lot of good things for this organization,” Cherington said. “We’ll wish him well, except when he’s playing against us.”

Lillibridge, 28, has played every position in the infield and outfield. He batted .258 with 13 home runs and 10 stolen bases in just 186 at-bats last year, but is hitting only .175 with no homers so far this season. He has no minor league options left.

The key cog of the trade is Stewart, 25, who will go to Pawtucket as a starter. He made his debut in the majors last year with the Blue Jays, then was traded to the White Sox in July. In 18 games this year (one start), he was 1-2 with a 6.00 ERA before getting sent to the minors last Tuesday. He has a career minor league ERA of 3.07, and has minor league options through 2013.

“We have scouted him since college (Texas Tech). We believe he can develop into a good major league starter,” Cherington said. “Needs a little more time in Triple-A to fine-tune things.”

Tejeda, 22, was put on the 40-man roster before the 2010 season but has struggled. He batted .249 last year in Portland and made 24 errors at second base. He was moved to left field this season and was batting .262 for the Sea Dogs.

Staff Writer Kevin Thomas can be contacted at 791-6411 or at:

kthomas@pressherald.com

Twitter: ClearTheBases