Antonelli was one of nine players sent to Minor League camp Sunday as the team pared its roster down to 29 players.
Other players who were reassigned include pitchers Cesar Carrillo, Ernesto Frieri, Mark Worrell and Greg Burke, infielder Logan Forsythe, outfielders Luis Durango and Aaron Cunningham and catcher Dusty Ryan.
All but Forsythe will begin the season with Triple-A Portland. Forsythe is likely headed to Double-A San Antonio.
Officially, Antonelli, Carrillo, Frieri, Durango, Cunningham and Ryan were optioned to Portland. Worrell, Burke and Forsythe were reassigned to Minor League camp.
Antonelli certainly accounted well for himself this spring after essentially falling off the Padres' radar after two miserable seasons offensively in 2008 and 2009. He revamped his swing and saw immediate results this spring.
Antonelli is hitting .378 this spring (14-for-37) with four doubles, one home run and eight RBIs.
"I said it before, but you can't play the way I have played forever or you won't be playing baseball," Antonelli said. "I feel like I did a pretty good job this spring. Even if my average didn't reflect it, I just wanted to hit some balls hard.
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"Hopefully, I can get ready now and try to make it up there [to San Diego]."
Several other players who were sent out had strong performances this spring, including Cunningham, who came over in the Kevin Kouzmanoff deal from the A's along with Jerry Hairston Jr. in January. Cunningham hit .286 and had seven stolen bases.
Durango hit .324 this spring with a team-leading nine stolen bases.
Worrell, who missed all of last season after having Tommy John surgery, pitched five scoreless innings.
Black had plenty of good things to say all spring about Forsythe, who is a third baseman but saw time at second base. There's no official position change in the works for him but there's a chance he could see more time there in San Antonio.
Forsythe hit .313 in 32 at-bats this spring.