Balfour has served as the team's primary closer for the past two seasons, saving 62 games for Oakland since 2012. His 2013 campaign earned him a spot on the AL All-Star team: 2.59 ERA with 38 saves, 72 strikeouts over 65 innings pitched.
The Athletics, however, do not normally spend big money on relief pitching. The team has stayed away from paying for a proven closer, choosing to plug someone into the role out of their bullpen. Oakland has found success with the strategy in the past; Andrew Bailey and Huston Street are other recent examples of relievers the team turned into closers.
Ryan Cook saved 14 games for the Athletics in 2012, and is a candidate to close if Balfour does not return. Sean Doolittle has also been effective in a set-up role the past two years, and could get a chance to pitch the ninth.