Cincinnati currently has a vacancy for the closer's role, but the Reds are looking at Marshall as a lefty set-up man.
The trade would fill a need for both teams. Appearing to be in a go-for-it mode for the 2012 division title, the Reds are flush with starting pitchers after acquiring Mat Latos from the Padres on Saturday.
The Cubs, undergoing a remodel under new president of baseball operations Theo Epstein and general manager Jed Hoyer, have some uncertainty at the end of their starting rotation. They would also covet Wood because he is under club control for at least five more seasons.
Compare that to Marshall, 29, who is a free agent after 2012. He has been one of baseball's most reliable relievers over the past two seasons, with a 2.45 ERA and 158 appearances in that span, second to Atlanta lefty Jonny Venters. Marshall will earn $3.1 million in 2012, the second season of a two-year deal he signed with the Cubs in January to cover his final two years of arbitration.
The Cubs would have much more control of Wood, 24, who does not project for free agency until October 2016. He was 6-6 with a 4.84 ERA in 22 games last season, 18 of them starts, and was twice demoted to the Minor Leagues.
Wood made his Major League debut at Wrigley Field on July 1, 2010, and gave up two hits over seven innings. He made one other start there in 2010 on Aug. 8, and picked up the win, giving up three earned runs on four hits over 6 1/3 innings.
Overall in 2010, Wood made a nice splash as a rookie with a 5-4 record and 3.51 ERA in 17 starts. But his down season in 2011, and the Reds willingness to deal him within the division, shows he lost some of his luster within the organization. He became more expendable after the Reds acquired Latos, giving Cincinnati a slew of starters including Latos, Johnny Cueto, Bronson Arroyo, Mike Leake, Homer Bailey and fireballing left-hander Aroldis Chapman, whom the Reds have been planning to convert from relief.
The Cubs, meanwhile, have some lefties who can step into the setup role in James Russell and Scott Maine, plus prospect Jeff Beliveau. Beliveau was named the Cubs' Minor League pitcher of the year after he held hitters to a .192 average in 53 appearances.
They also have the makings of a solid starting rotation with right-handers Matt Garza, Ryan Dempster and Randy Wells currently in the three spots, Carlos Zambrano still in the mix despite spending the end of last season on the suspended list and Jeff Samardzija an option to convert from relief.
But Garza has appeared in trade rumors and Zambrano is a wild card, so Epstein and Hoyer have been looking at available starters. Among the free agents they reportedly have contacted are left-handers Paul Maholm and Jeff Francis.