By Matt Snyder

The Cubs have agreed to trade volatile and highly-paid starting pitcher Carlos Zambrano to the Marlins, with an announcement coming as soon as Thursday, CBSSports.com insider Jon Heyman has learned. The preliminary deal is that the Cubs would pick up the overwhelming majority of the $18 million Zambrano is owed for 2012 and that starting pitcher Chris Volstad is headed to the Cubs. Multiple reports indicate the Cubs will pay $15 million to the Marlins.

New Cubs president Theo Epstein has been publicly saying he'd give Zambrano one last chance in Chicago throughout the entire offseason. In fact, earlier Wednesday on a Chicago radio show, Epstein said that he was "skeptical" but would give Zambrano a chance to prove he's changed. It's not too surprising that he would be putting off that vibe publicly while privately trying to rid his club of a past cancer, though.

For stretches, when Zambrano could remain healthy and well-behaved, he produced as a frontline starting pitcher. He's a three-time All-Star who finished exactly fifth three times in NL Cy Young voting. After anger management sessions midseason in 2010, he closed the season in lights-out fashion, going 8-0 with a 1.24 ERA. But then Zambrano walked out on his team last August after getting ejected from a game in Atlanta. Then-general manager Jim Hendry basically kicked Zambrano off the team, sending him away and placing him on the restricted list.

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Considering this and the fact that Zambrano is owed such a lofty salary next season, it's easy to see why Epstein wasn't so quick to cut ties with Zambrano for nothing. But it's possible Zambrano's long-time friendship with new Marlins manager Ozzie Guillen made the deal easier to consummate.

Guillen was specifically asked about Zambrano during the Winter Meetings and said the two exchange text messages everyday.

"Every time I talk to Zambrano," Guillen said, "all of a sudden people think I'm talking about contracts or moving him to the Marlins. That's tampering."

He then joked: "We do that on the side, not around people."

So while Guillen hasn't publicly courted Zambrano, it's obvious the two are great friends and would love to work with each other. Thus, the no-trade clause shouldn't be much of an issue.

The Marlins already have a top two in the rotation in Josh Johnson and Mark Buehrle. With Anibal Sanchez and Ricky Nolasco around, they could feasibly slot Zambrano as the fifth starter in an attempt to alleviate any pressure he'd put on himself.

Volstad, 25, was 5-13 with a 4.89 ERA and 1.43 WHIP last season. He was once a fairly-highly touted prospect but hasn't made a great transition to the majors, aside from a solid rookie campaign (6-4, 2.88 ERA, 1.33 WHIP in 2008).

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