Approximately 28 teams scouted Castillo during his workout last month, and a smaller group of clubs followed up with individual workouts. The Tigers had a handful of evaluators there, then scouted him more closely in an individual workout last Sunday in Miami.
The Red Sox and Yankees are among the leading contenders for Castillo's services. However, as Joel Sherman of the New York Post reported, the Tigers are also seen as "major players" for Castillo by others in the industry.
Whoever signs Castillo will get a speedy, athletic outfielder with surprising power -- who has drawn comparisons with Brett Gardner and Jacoby Ellsbury in terms of style of play -- and is seen as close to big league ready. Whether the 27-year-old would provide that type of impact this season has been debated. While he's an older, more seasoned talent, he also hasn't played competitive baseball in more than a year.
Whether or not Castillo could contribute down the stretch, he fits a need for the Tigers, who have a long-term void in center field since trading Austin Jackson to Seattle. Top center field prospect Derek Hill, Detroit's first-round Draft pick this season, is at least a few years away. Detroit's better prospects in the middle and upper levels are generally seen as corner outfielders.
Moreover, while bidding on Castillo could skyrocket, it beats the free-agent market this winter, where Colby Rasmus projects to be the top center fielder available.
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. Matt Slovin contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.