The Giants have relied on pitching for their recent run of success, but in 2015, it's been a weakness. Since 2010, they've relied primarily on Jeremy Affeldt, Javier Lopez, Sergio Romo, and Santiago Casilla. While three of the "core four" have performed well, for the most part, Affeldt has been a disappointment, which could lead the Giants to target outside help; and according to Jon Morosi, they're aiming sky high.
If he's available, Aroldis Chapman would be the golden goose of relief pitchers on the market. He has a fastball that has reached 105 MPH, and with a career strikeout rate of 15.41, he would fit nicely into any bullpen. The Giants currently rank 22nd in terms of reliever fWAR, and if they can't acquire Chapman, it stands to reason that they'd turn their attention elsewhere for an upgrade.
It's difficult to predict what type of package the Reds would ask for, but the Giants have balked at anything involving their top prospect Tyler Beede. They also recently halted negotiations concerning a starting pitcher when Lucius Fox was brought up. The Reds could be interested in Andrew Susac, as Devin Mesoraco might be better suited for a role in the outfield, but as Morosi reported, no names have been exchanged yet.