Rusney Castillo is expected to decide his Major League future no later than this weekend and the Boston Red Sox and Detroit Tigers are the front-runners for his services, according to sources.

A source with direct knowledge of the negotiations said the Red Sox are "optimistic" they will ultimately sign the Cuban outfielder.

Boston wants to boost their outfield going forward, while Detroit has had a hole in the outfield since trading Austin Jackson as part of the David Price deal last month. Castillo could make an impact immediately.