Justin Upton has yet to announce a decision, but it's becoming more and more likely that he'll exercise the opt-out clause in his contract and become a free agent, according to a source.

Upton must decide on his opt-out within three days of the conclusion of the World Series. He is due $88.5 million over the next four seasons.

He played the final 27 games of the season with the Los Angeles Angels following a late August trade from the Detroit Tigers.

Upton had a career year, establishing highs in home runs (35), RBIs (109) and OPS (.901).