CBS Sports first reported on Tuesday that Fielder decided to turn down offers from the Rangers, Nationals, and others to sign with a team that hadn't been mentioned throughout the off-season.
Yahoo Sports' Tim Brown also reported that the Tigers were close to coming to a deal with the former Milwaukee Brewers slugger.
The deal comes as a complete shock to many that have followed the Fielder sweepstakes for the past few months. The Washington Nationals have long been considered the favorite to sign the 27-year old, but reportedly balked at going beyond a six-year deal.
Fielder, who hit 38 home runs and batted in 120 RBIs last year, was considered one of the elite free agents going into the winter. From the beginning Fielder and his agent, Scott Boras, had hinted that they were looking for a $200 million-plus deal and apparently got it.
The Tigers were never considered a major contender for Fielder, but might have been rushed into action after slugger Victor Martinez tore his ACL. Martinez, who will miss the entire 2012 season, provided lineup protection for Miguel Cabrera and was a valuable part of the organization last year.
Fielder will assume the starting first baseman role, according to CBS Sports' Jon Heyman, and Cabrera will be forced to move to another position -- possibly as a permanent DH.
The Texas Rangers, Seattle Mariners, and Baltimore Orioles had also been recently mentioned as possible landing spots before Fielder reportedly decided on Detroit.