Red Sox outfielder Jason Bay
Jason Bay isn’t technically a one-year wonder because he did play an extra half-season, but this is my list so I make the rules.
Bay came to town from the Pirates as part of the 2008 trade deadline, three-team deal that sent Manny Ramirez to the Dodgers. Bay had big shoes to fill in left field and he did so admirably.
He ended the year with an .897 OPS for the Red Sox in 49 games during the regular season along with 14 hits and three home runs in the playoffs that fall.
Bay followed up that half-season with an excellent 2009 season. He lead the team in home runs, RBI, walks and was second to Kevin Youkilis in SLG and OPS. He was an All-Star, Silver Slugger, and finished 7th in MVP voting for his efforts that year.
However, in the 2009 ALDS, Bay couldn’t match his production from the season or playoffs prior as the Red Sox were swept by the Angels. Bay went on to sign with the Mets, but wasn’t able to recreate the success he found in Boston and ultimately retired in 2013.