Ken Rosenthal of FOXSports.com reports that the Cubs are drawing heavy trade interest in left-hander Sean Marshall. Marshall has emerged as one of the better relievers in the game over the past two seasons, posting a 2.45 ERA and 169/42 K/BB ratio over 150 1/3 innings. The 29-year-old southpaw is due $3.1 million in 2012 and is scheduled to hit free agency next offseason, so the Cubs might cash him in for prospects if the right offer comes along.