Despite agreeing to sign Grant Balfour, the Athletics still aren't done trying to upgrade their bullpen. Ken Rosenthal of FOX Sports says that Oakland is "pushing" to sign Brian Fuentes, and he reiterates that the Blue Jays are a serious suitor for his services as well.
A multitude of teams have expressed interest in the free agent lefty this offseason, and with Balfour and Rafael Soriano now off the board, Fuentes has emerged as arguably the best free agent reliever available. Oakland already has two effective left-handers in its bullpen (Craig Breslow and Jerry Blevins), but there's no such thing as too many quality relievers.
We've also seen young, cost-controlled relievers traded quite a bit this offseason, including in deals for J.J. Hardy, Mark Reynolds, Jason Bartlett, and Cameron Maybin. Oakland could turn around and deal Blevins, Joey Devine, or Brad Ziegler for help at another position now or before the deadline. The market is certainly there, and adding Fuentes would help maintain the team's relief depth.