Ryan Cook might have been the Oakland Athletics All-Star representative in July, but if the bullpen arms were ranked today, he wouldn't be No. 1. There are currently eight relievers. As a staff, they have the third best ERA in Major League Baseball. They're also tied for first in most wins and lowest opposing batting average. Clearly, they're talented. The members of Oakland's bullpen fair well against the rest of the league—so how do they stack up against each other? The heaviest factors are total runs allowed and ERA.