Colorado Rockies trade rumors: Breaking down the St. Louis Cardinals' best prospects

As reported Thursday morning here at Purple Row, the St. Louis Cardinals have been talking with the Colorado Rockies about possibly acquiring one of the Rockies' left-handed outfielders. Since signing Mike Leake to a five-year, $80 million contract, it appears the Cardinals may improve their outfield through trades rather free agency, and hearing they've inquired on Carlos Gonzalez, Charlie Blackmon, or Corey Dickerson makes sense.

Leake solidifies the Cardinals' rotation with Adam Wainwright, Jaime Garcia, Michael Wacha, and Carlos Martinez already in place. Combined with the hopeful return of Lance Lynn from injury before the 2017 season, this could mean the Cardinals may be open to trading some of their young arms to fill the hole left when Jason Heyward signed with the Chicago Cubs.

The Cardinals are not planning on trading any of their big league pitching, according to FOX Sports' Ken Rosenthal. So assuming the Rockies still want pitching — which is always a safe assumption — let's look at some prospects that could headline a deal.

Alexander Reyes

Reyes, 21, is the current jewel of the Cards' farm system, though there are some concerns. The right-handed pitcher is considered by most to be at least a 60 future value prospect (on a 20-80 scale), and a top-20 prospect in all of baseball. Armed with 70-grade fastball, Reyes struck out a phenomenal 151 hitters in 101 innings in 2015 (13.5 K/9), though he did also walk 49 (4.7 BB/9). Reyes followed that up in the Arizona Fall League with an abbreviated 15-inning season, logging 14 strikeouts and ten walks.

Reyes' fastball is by far his best tool, sitting in the mid-90s consistently with the ability to top 100 mph on occasion. His next best pitch is a curveball that he throws in the mid-70s with sharp movement. His changeup is still a work in progress, though it has shown some signs of eventually being an above-average offering. Reyes also has an easy, repeatable delivery.

Reyes' biggest weakness right now is by far his command, as evidence by his minor league career walk rate of 4.6 BB/9. While the stuff is obviously great, as we've seen many times before it won't matter if it can't be controlled. Also of note, Reyes will be serving a 50-game suspension next year because of a positive drug test for marijuana. However, once Reyes is added to a 40-man Major League roster, he is no longer subject to testing or discipline for marijuana use.

Tim Cooney

Cooney, 25, is rated by Baseball America as the Cardinals' second-best prospect. Last year, Cooney had a solid Triple-A season that led to his first MLB action where he acquitted himself fairly well. At Triple-A Memphis, the left-handed pitcher struck out only 6.4 batters per nine innings, but also limited walks to only 1.6 per nine innings. At the big league level, Cooney made six starts covering 31⅓ innings, striking out 29 and walking 10.

Cooney's best pitch is a great sinking change-up that he's shown a willingness to use as much as needed. The rest of his four pitch repertoire is fairly average, but good control makes it all play up. Cooney's delivery is low effort and makes his low-90s fastball appear faster to hitters, as well. A Wake Forest University product, Cooney was taken by the Cardinals in the third round of the 2012 draft.

Jack Flaherty

Flaherty, 20, was a first-round pick in 2014 (34th overall) by the Cardinals out of a high school in southern California, and is further away from the big leagues than Reyes and Cooney. Since being drafted, Flaherty has performed extremely well while transitioning to being a full-time starter. In 2015, the right handed-pitcher struck out 97 hitters and walked just 31 over 95 innings at Low-A Peoria, playing against opponents on average three years older than him.

Since Flaherty is very young, and he wasn't just a pitcher in high school, his stuff may not be as polished as an older or more developed hurler. At this point, his changeup is his best pitch, though there is reasonable expectation he will continue to add velocity to a fastball that sits at 93 mph. A good slider and a developing curveball give him at worse a three-pitch mix that could still develop into the four-pitch repertoire ideal in a starting pitcher.

Luke Weaver

Weaver, 22, was also a first-round pick of the Cardinals in 2014 (27th overall). Drafted out of Florida State University, the right-handed pitcher was originally expected to be taken much higher in the first round, but fell after a disappointing junior season. After a rough first professional season, too, Weaver bounced back with a good 2015 campaign at High-A Palm Beach, where he started 19 games and logged 7.5 K/9 against 1.6 BB/9 with a 1.62 ERA and 1.111 WHIP.

Like so many other Cardinals pitching prospects, Weaver's best pitch is his changeup, though his fastball can top out at 97 mph and sits comfortably in the mid-90s with good movement and sink. Like most big-college power pitchers drafted in the early rounds, Weaver's got a good feel for his pitches and profiles as a third or fourth starter in the big leagues a few years from now.

Marco Gonzales

Gonzales, 23, is the son of Rockies minor league pitching coach Frank Gonzales and played high school ball in Colorado before attending Gonzaga University. Drafted as a highly-polished pitcher, Gonzales made it to the Major Leagues only a year after he turned pro, and he was a playoff hero for St. Louis against the Dodgers in 2014. However in the past year, Gonzales really struggled in Triple-A, starting 14 games and logging a 1.66 WHIP and a .323 opponents' batting average with just 51 strikeouts in 69 innings.

Gonzales' best pitch is also a changeup, and he has very good control for his age and level. However, the rest of his stuff doesn't seem solid enough to keep Major League hitters off balance right now, as his fastball struggles to consistently top 90 mph. Gonzales also struggled with shoulder soreness in 2015, which ought to be a red flag for any pitching prospect in trade talks.

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Besides these pitching prospects, there are also some interesting position players that could attract the Rockies' attentions.

Magneuris Sierra

Sierra, 19, is extremely green in pro baseball years, but has the makings of a five-tool outfielder should he develop the way the Cardinals' front office hopes. Signed out of the Dominican Republic in 2012, Sierra has had both good and bad results at various levels of the Cards' minor league system, while generally playing against competition two or more years older than him. He slashed .315/.371/.394 at Rookie-Level Johnson City in 53 games in 2015 before being promoted to Low-A Peoria and struggling, slashing just .191/.219/.247 in 178 at-bats. He'll most likely repeat the level in 2016.

The left-handed hitter has a very quick bat and a fairly flat swing that generates a lot of line drives. As he continues to physically develop, it's not hard to project 15-20 home run power and possibly more if he adds some lift to his swing. With plus speed and a strong arm, Sierra is equipped to play all three outfield positions, though center field would take the best advantage of his speed at this point in his career.

Nick Plummer

Plummer, 19, was drafted in the first round (23rd overall) in 2015 out of a high school in Michigan. The left-handed hitting outfielder slashed .228/.379/.344 in rookie ball demonstrating that while he did have some contact issues (56 strikeouts in 180 at-bats), he has power (eight doubles, five triples and a home run) and an extremely patient approach at the plate (39 walks) in spades.

Plummer is expected to develop into a solid mid-lineup left-fielder, since he doesn't seem to have enough speed to play center, and lacks the arm strength to play right field. However, he does have a very quick swing and a good understanding of the strike zone, and should develop into a good hitter as he ages.

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Obviously, a note to remember: a hypothetical Rockies haul in return for sending a big league outfielder to the Cards will probably only include one or at most two of these players, depending on who the Cards are most willing to offer; a larger package might include players further down St. Louis' prospect list, in what would likely have to be a multi-player deal depending on specifics.

Even so, hopefully this gives you a better understanding of who in the Cardinals' system ought to be attracting the Rockies and general manager Jeff Bridich during preliminary trade talks.