Jeremy Giambi's departure will make room for Adam Piatt in Oakland. (Brian Kersey/AP)

Oakland manager Art Howe warned the team on Sunday that moves were imminent, and suddenly the A's have four new faces and a dramatically different team.

"They're making changes," said third baseman Eric Chavez. "They said they were, and they weren't bluffing."

Eric Chavez   /   3B
	Height: 6'0" Weight: 204 Bats/Throws: L/R More info: Player page Stats Splits Hit chart Athletics site

With the departure of Giambi, who said he was stunned -- "very much so" -- by the trade, the A's said goodbye to their starting left fielder. On Tuesday they said goodbye to starting first baseman Carlos Peña, second baseman and fan favorite Frank Menechino, and oft-used-but-ineffective righty reliever Jeff Tam.

"It was pretty shocking," said Chavez. "I keep hearing there might be some more stuff going on, so you kind of come in and start looking around at the lockers to make sure everyone's still here."

Giambi was on Howe's lineup card Wednesday morning, but general manager Billy Beane announced the trade about 30 minutes before the game.

Giambi was replaced in the lineup by Larry Sutton, who was one of the Tuesday call-ups, and Sutton responded with a three-run homer and a single. Equally significant was that Sutton recorded Oakland's first outfield assist of the season; Giambi's greatest shortcoming is his defense, particularly a weak throwing arm.

"Early on he showed some improvement, but we needed an upgrade there," Beane said of Giambi's glovework, "If we're going to at times struggle to score runs, we need to at least do something to prevent them defensively, and this certainly does that."

Sutton, however, will probably see less time in left than will another one of Tuesday's call-ups, Adam Piatt.

Piatt, 26, started Wednesday in right field while regular right fielder Jermaine Dye served as designated hitter. Beane said the trading of Giambi was intended to give Piatt regular playing time and help keep David Justice healthy once he returns from the disabled list.

"With David coming back soon, we'll have a little bit of a glut at DH," Beane said, "This will get Adam some at-bats and keep David fresh. With either Adam or David out there (in left), it will be an improvement defensively."

Piatt, who was named Minor League Player of the Year in 1999, was up with Oakland for part of 2000 and 2001 but missed much of last year with viral meningitis and missed most of Spring Training this year with a strained rib-cage muscle.

"We've always been very curious to see what he can do if given the opportunity," Beane said.

The other Tuesday call-up, second baseman Esteban German, will take over as Oakland's starter, but Randy Velarde will get the occasional start when matchups dictate.

"Randy's going to get plenty of playing time," Beane said.

AUDIO: MLB.com's Mychael Urban discusses the A's roster moves

Giambi, 27, is hitting .274 with eight homers and 17 RBIs in 42 games and had career highs in homers (12) and RBIs (57) while batting .274 in 124 games for Oakland last season.

In a farewell press conference during Wednesday's game, Giambi teared up on occasion and said he'll miss playing in Oakland.

AUDIO: Jeremy Giambi addresses the media after the trade

"This is a great group of guys with a great chemistry," Giambi said. "I liked playing here. ... They have a great core of guys here with the pitching and Chavez and [Miguel] Tejada and Terrence [Long] ... Maybe they just felt like I didn't fit into that core."

Giambi also defended his defense: "I feel like I worked hard out there and made some great catches. I feel like I was doing a good job out there."

Mabry, 31, can play both corner outfield positions, as well as first and third base. His best season was with St. Louis in 1996, when he hit .297 with 13 homers and 74 RBIs.

"They're getting a good guy in John Mabry," said Phillies GM Ed Wade. "One of the big reasons why John made our club out of Spring Training was his makeup, and I think that's what the A's were looking for. ... Hopefully, it's a good deal for both clubs."

Mabry is hitting .286 with three RBIs and zero home runs in 21 games but is 5-for-16 with two RBIs as a pinch hitter.

"Mabry got some big hits for us in the role that he was in here and didn't play very much," Wade said. "Going over there, he may get a chance to play more and be fresh. I'm happy with our part of the deal and I'm sure they are."

"He'll be very much a role player here," Beane said. "He gives us significant versatility ... He's a bench guy."

The deal marks the second time in the last six months a Giambi has left the Bay Area. Giambi's brother, Jason, signed a free-agent deal with the Yankees over the winter.

"Today was the first game since I've been here that I didn't have a Giambi to put in the lineup," said Howe, who is in his seventh season with Oakland. "It's gonna be different.

"I told [the players] some changes are going to take place. I didn't lie."

Mychael Urban covers the Oakland A’s for MLB.com and can be reached at murban@oaklandathletics.com. Ken Mandel and Kevin Czerwinski of MLB.com contributed to this report, which was not subject to approval by Major League Baseball or its clubs.