5. Mark Teixeira: Eight Years, $180 Million
When the New York Yankees brought Mark Teixeira in to finish their 2008-09 offseason, it was genuinely stunning. It was almost Carlos Correa leaving San Francisco-esque, except without a deal in hand and a Tweet already drafted. It would've broken the internet, if there'd been a modern internet to break.
Teixeira was viewed as the Red Sox' counter to New York's Sabathia/Burnett duo, and would've been right in line with their recent acquisitions of Mike Lowell, Jason Bay, and any number of bland, non-erratic contributors to help get the Manny Ramírez taste out of their mouths.
Tex's 2009 season was special (39 bombs, 122 RBI, second-place MVP finish, 156 games played), and he remained durable for the next two seasons, though his average dipped from .292 to .256 to .248. In 2012, he battled lingering ailments before tearing his wrist sheath the next season, knocking his career officially off course.
He made the 2015 All-Star team and slugged 31 bombs, but was a relative shell of himself prior to his 2016 retirement. Again, for the hundredth time on this list, though ... do what you did in '09 and win a title and you're worth the bumps and bruises on the back end.