Gregg served as the Cubs' closer in 2009 before signing with the Blue Jays in 2010 and inking a two-year deal with the Orioles that covered the 2011-12 seasons. He returned to the Cubs on a minor league deal this April and now finds himself in the midst of an unlikely career year at age 35.
Gregg has pitched to an immaculate 1.11 ERA with 9.6 K/9 and 2.6 BB/9 with 11 saves in 24 1/3 innings since returning to the Cubs. That ERA is likely unsustainable, but even advanced metrics like FIP (2.31), xFIP (3.05) and SIERA (2.79) feel that Gregg's work this year has truly been in the upper echelon of Major League relievers.
Gregg could serve as a bargain bullpen upgrade for teams that don't wish to meet the steep asking price on players like Jesse Crain and Jonathan Papelbon (if he does indeed become available). Gregg ranks fourth in FIP, xFIP and WAR among relief trade candidates according to the custom Fangraphs leaderboard compiled yesterday by MLBTR's Tim Dierkes.