Wait, he was a Red Sox shortstop?
Edgar Renteria (2005)
Picture this: you've just snapped an 86-year long curse, the feelings around the team have never been better, and... you don't have a shortstop for the next season. No worries! All you need to do is go out and sign the star shortstop of the team you just beat in the World Series the previous year!
Edgar Renteria came to Boston for the 2005 season with fans hoping he could hold down the position for a little while, but that's not what fans received. What fans got was a below-average season at the plate, Renteria's worst fielding season of his career (which earned him the affectionate nickname Rent-a-Wreck), and a sweep at the hands of the eventual-champion Chicago White Sox in that year's ALDS. Probably the most disappointing entry in this lineup, Renteria never reached the same production he had in St. Louis, and the Sox were smart to trade him after the 2005 season.
Honorable Mentions: Another position with consistent stretches of stalwarts, the only one-off type seasons that I feel could have also worked would have been guys like Mike Aviles, Alex Gonzalez, current manager Alex Cora, but Renteria was the best overall player that I felt fit this team.