On Wednesday morning, the A's dealt starter/reliever Drew Pomeranz to San Diego for first baseman Yonder Alonso and lefty reliever Marc Rzepczynski.
Following the deal, A's general manager David Forst told reporters that beefing up the bullpen will be a priority when the annual Winter Meeting convene in Nashville next week.
One name to keep an eye on is veteran righthanded reliever Ryan Madson.
According to MLB.com's Jane Lee, the A's are showing interest in Madson, and one source said they are a "legitimate suitor" for the 35-year-old.
After missing three full seasons with arm injuries, Madson resurfaced with Kansas City in 2015 and put together a season reminicent of his pre-injury days.
In 68 appearances for the Royals, Madson compiled a 2.13 ERA with 58 strikeouts in 63.1 innings pitched.
In addition to Rzepczynski, the A's also acquired righthanded setup pitcher Liam Hendriks from Toronto in exchange for Jesse Chavez on Nov. 20.