The Rule 5 Draft takes place next month on the final day of baseball's annual Winter Meetings, and any player taken must remain on his new team's active roster or disabled list all season, or be offered back to his original club for $25,000.
The move left Baltimore's 40-man roster at 39, and though the Orioles were prohibited from adding another player from within the organization until the Rule 5 Draft is over, they did add Antonelli on Monday after the former first-rounder signed a Major League contract.
Antonelli, 26, was the Padres' first-round selection (17th overall) in the 2006 First-Year Player Draft. He spent 2011 with Double-A Harrisburg (four games) and Triple-A Syracuse (86 games) in the Nationals' system, batting a combined .298/.390/.457 with eight home runs and 31 RBIs, finishing in the Top 10 of the International League in on-base percentage. Antonelli is a career .264/.373/.406 hitter in 469 career Minor League games over six seasons. He made his Major League debut in 2008 with San Diego, batting .193/.292/.281 in 21 games.
"We are pleased to bring Matt to the organization," said Orioles executive vice president of baseball operations, Dan Duquette. "He is a versatile Major League player who has a good offensive approach and strong defensive skills at both third and second base."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.