The Cubs are likely to trade one or both of Jeff Samardzija and Jason Hammel. Several teams have already been mentioned as potential suitors for the Chicago right handers, including the Giants, Blue Jays, Marlins, and Orioles. Gordon Wittenmyer of the Chicago Sun-Times believes the Mariners are a part of that group as well. He mentioned Hammel in connection with the M's, stating that at least one Major League source believes Seattle will acquire him.
Hammel, 31, is putting together a career season, posting 2.81 ERA over 83⅓ innings with 76 strikeouts and just 18 walks. His sub-1.00 WHIP pops out at you, but it has been aided by career-lows in BABIP and home run-flyball percentage. Despite that relative luck, Hammel's fielding-independent pitching (FIP) sits at 3.02 and his expected fielding-independent pitching (xFIP) is 3.47, so his success appears to be somewhat sustainable. Hammel will be a free agent after the season, so the Cubs' asking price for him will surely be less taxing than Samardzija's.
Samardzija, 29, won't be a free agent until after next year, so the Cubs might still decide to hang onto him in hopes of extending his contract for a few more years. However, the potential for a significant return on the trade market has caused them to begin fielding offers. He's in the midst of a career year as well. In 91 innings, he has a 2.77 ERA and he has walked just seven percent of the hitters he has faced, a career-best. The Cubs would probably open negotiations asking for Taijuan Walker -- who is about to return to majors from the disabled list. It seems highly unlikely that the M's would consider trading their top prospect.