By Jamal Collier

The free-agent market for outfielders is likely to be the next to heat up, now that Jason Heyward has agreed to a deal with the Cubs. There are plenty of good options for teams searching for improvement. Yoenis Cespedes, Justin Upton and Alex Gordon are the next biggest pieces available, with Denard Span, Gerardo Parra and Dexter Fowler also on the board as less expensive, but still useful pieces.

Now the Rockies seem prepared to inject another prize into the mix. They are reportedly open to trading any of their three outfielders, the most attractive piece being Carlos Gonzalez. With the improvements the D-backs have already made combined with the fact that the Dodgers and Giants have owned the National League West recently, the Rockies seem unlikely to compete in 2016. And ever since Colorado traded Troy Tulowitzki to Toronto last July, it's been assumed that Gonzalez would be the next to go.

The Rockies can expect a nice package in return for Gonzalez. He comes at an attractive price -- he's owed $17 million in 2016 and $20 million in 2017 -- especially considering the contracts the other free agent outfielders will demand. He is also coming off an impressive 2015 where he batted .271/.325/.540 with 40 homers and a .864 OPS, proving that when he stays healthy he can still be a game-changing bat in the middle of the lineup. The problem has been his issues with injuries, which cost him a combined 144 games in 2013-14 before he played 153 games last season.

Still, CarGo's 2015 means the Rockies could command a package for him comparable with to what they got for Tulowitzki, who was traded for Jose Reyes and three legitimate right-handed pitching prospects, all of whom rank within the Rockies' top 20 prospects, as rated by MLB.com. Especially considering some of the prospects and former high draft picks already traded during this offseason, the Rox could cash in big time for Gonzalez.

Here are some teams that could be a good fit.

Cardinals

After losing Heyward to their division rival Cubs, what better way could the Cards answer? St. Louis has already reportedly finished as the runner-up to three big-name free agents -- Heyward, David Price and Jeff Samardzija -- so the team has the money to do something impactful. Gonzalez would be a power bat in the middle of their lineup, moving Stephen Piscotty to first base. The Cardinals also have a strong farm system, which is what separates them from the rest of the pack, although they are usually less willing to deal their top prospects, such as right-hander Alex Reyes, who is ranked as the No. 16 overall prospect in baseball according to MLB.com.

Nationals

The Nats have reportedly been one of the teams most interested in Gonzalez. If Washington is unable to re-sign Span, its outfield becomes thin, with the exception of Bryce Harper. Jayson Werth, 36, posted a .685 OPS last season, and has struggled with injuries. Michael Taylor was a top prospect, but posted a .640 OPS as a rookie. So Gonzalez would slot in as a nice complement to Harper in the Washington lineup and provide a left-handed hitter to balance things out. That the Nationals are involved at all is intriguing considering they still owe Werth $42 million over the next two years. Gonzalez has not appeared in center field since 2011, so maybe that means the Nats believe Harper can play center field while Gonzalez moves to right.

Mets

Cespedes helped spark the Mets to a World Series run, but New York seems comfortable losing him to free agency. They will still need to replace his production at some point and would have the pieces necessary to make a trade again. How willing they will be to do so is another story. The Mets have been reluctant to trade any of their four young starting pitchers -- Matt Harvey, Jacob deGrom, Noah Syndergaard or Steven Matz -- and a deal would almost certainly have to include one of them. Maybe the Mets would be open to trading Zack Wheeler, but then the Rockies would have to be willing to take on a pitcher coming off Tommy John surgery. If Colorado does not have any luck trading CarGo this offseason, perhaps a deal before the Trade Deadline involving these two teams could be possible.

Others to consider:

Giants: There is a need on San Francisco's side, but Colorado could be reluctant to trade Gonzalez within the division.

Orioles: Baltimore could become aggressive on the trade market to fill a huge gap in its lineup if it does not sign one of the big free agent outfielders and cannot re-sign first baseman Chris Davis.

Angels: Los Angeles is still searching for a left fielder and would love another productive hitter to go in the middle of its lineup to provide protection for Mike Trout and Albert Pujols.

Each team seems certain to add an outfielder during the next few weeks and will have to decide if they would rather deal prospects instead of shelling out the money for a long contract. Still, if the Rockies are looking to make a deal, they should have a number of suitors.

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Jamal Collier is a reporter for MLB.com. Follow him on Twitter at @jamalcollier.