Antonelli was originally drafted as a third baseman by the San Diego Padres with the 17th pick of the 2006 Major League Baseball Draft. In July, Antonelli was named the best second base prospect in the minors by Kevin Goldstein of Baseball Prospectus. In November 2007, Antonelli was ranked as the #1 second base prospect and #27 prospect overall in baseball, on a list polling 20 members of the scouting community and compiled by Jonathan Mayo of minorleaguebaseball.com 2008 Before the 2007 season, Antonelli was not considered to have much power potential after having zero home runs in over 200 professional at bats in. However, he hit 14 home runs in 82 games for High A Lake Elsinore, before moving up to Double A San Antonio Missions to finish the season. In 534 at-bats between the two levels, Antonelli finished with a slash line of.304/.404/.491 with 21 home runs and 25 stolen bases along with a 94/83 K/BB ratio. He won the Texas League Championship with the Missions in 2007. In 2008, Antonelli played for the Padres' AAA farm club, the Portland Beavers. He struggled at the plate most of the year, hitting just.215, but kept his good eye and ended up with 76 walks. In August he found some success, hitting.290 for the month, with 4 home runs and a.393 OBP. Antonelli was called up to the Padres on September 1, 2008, where he promptly laced a single off Greg Maddux of the Dodgers for his first hit in the major leagues. He then went hitless in his next 20 at bats, but then got 7 hits in his next 13 at-bats with 3 walks, including his first home run, on September 15, off of Colorado Rockies pitcher Jason Hirsh. He was unable to earn another big league promotion with the club and granted free agency at the end of the 2010 season.
He signed as a minor league free agent with the Washington Nationals on December 17, 2010 and spent the season with the AA Harrisburg Senators and AAA Syracuse Chiefs.
On November 21, 2011, Antonelli signed with the Baltimore Orioles. He was added to the team's 40-man roster. On May 13, 2012, the Orioles designated him for assignment.
On May 17, the New York Yankees claimed Antonelli off waivers from the Baltimore Orioles. He was designated for assignment on July 1 and released on July 5.
Antonelli signed a minor league contract with the Cleveland Indians in January 2013. After appearing in 3 games with Triple-A Columbus, he retired on July 17.
Post-baseball career
After retiring, Antonelli received several calls from independent league teams. However, he declined all of those offers due to his injury history and his belief he could not make it back to the Major Leagues, and decided to focus on a potential career of coaching. Antonelli is well known for his YouTube channel, , for which he makes baseball-related videos. Recently, Antonelli has started a Road To The Show series on his channel which gained popularity and slowly spiked his subscriber count. The channel has more than 148,000 subscribers and over 31,150,000 views as of May 2020. He also was an assistant baseball coach at the College of the Holy Cross and Wake Forest University.
