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9/3/2014 11:28 A.M. ET

Pipeline Perspectives: Heaney has complete package

Despite early big league struggles, Marlins hurler best lefty pitcher other than Urias

There's a good amount of subjectivity regarding baseball prospects. With the evaluation of talent being in the eye of the beholder, finding consensus is often difficult. Even Jim Callis and Jonathan Mayo of MLBPipeline.com don't always see eye to eye. They discuss their viewpoints regularly in a feature called Pipeline Perspectives. Submit a topic for them to debate.

Sometimes, a prospect's stock can be disproportionately affected by an unsuccessful big league debut, no matter how brief it may be. I want you to keep that in mind as we discuss this week's topic in Pipeline Perspectives.

Both Jim and I agree that the Dodgers' Julio Urias is the best left-handed pitching prospect in the game. Who comes next on that list is up for debate. While Jim is going with recent draftee Carlos Rodon of the White Sox, I'm sticking with Marlins southpaw Andrew Heaney.

I say sticking with because Heaney was ranked as our No. 1 left-handed pitching prospect before the 2014 season began. The current Top 10 has him at No. 2, one spot ahead of Rodon, the No. 3 pick in the Draft. Truth be told, there isn't a whole lot separating Heaney, Rodon and even the No. 4 southpaw, Henry Owens of the Red Sox (No. 5 Daniel Norris isn't too far behind, either). This week's perspective is more a matter of personal preference than any one tool that makes one clearly better than the other.

Heaney certainly hasn't done anything to diminish his value as a prospect. He's actually improved his standing in the Top 100, going from No. 29 at the start of the season to No. 21 now. Starting the year in Double-A, but moving quickly to Triple-A, the 2012 first-rounder led the organization in strikeouts, finished third in batting average against and WHIP and fourth in ERA.

Heaney put up all those numbers all while fulfilling his billing as an advanced college lefty who would get to the big leagues quickly. He made his Major League debut just two years after being drafted. That first start was a good one, with Heaney giving up just one run over six innings. The next three, however, weren't as successful, and he was back in Triple-A by mid-July.

After taking a little time to readjust, Heaney threw well down the stretch, with his best outing coming on Aug. 17, an eight-inning, one-hit, no-run effort. That, combined with a solid start just prior, earned him Pipeline Pitcher of the Week honors.

Now Heaney is back in the big leagues, with a chance to perhaps take the ailing Henderson Alvarez's spot in the Marlins' rotation. This brings me back to my first point, about big league debuts sometimes clouding one's judgment about a prospect. I get the sense that because he wasn't effective right out of the gate, Heaney dropped in the eyes of some.

Heaney is still very much the same pitcher who topped our lefty list at the start of the year, perhaps wiser because of the adversity he faced. The long ball really hurt him during his debut, as he allowed five homers in four starts. That trouble followed Heaney back down to Triple-A at first, but then he recovered, allowing just two home runs in his six August starts (though he gave up two more in his final start of the year). That's a home run rate of just 0.5 per nine innings, much better than the 2.2 from his first Major League stint.

That one stat isn't a huge indicator, but it does speak to Heaney's ability to make adjustments, something that will serve him well this month and well beyond that. And we're not talking about a soft-tossing, touch-and-feel southpaw here. Don't confuse "quick to the big leagues advanced college left-hander" with "finesse lefty."

Heaney combines outstanding command and feel for pitching with plus stuff. That's what makes him one of the best pitching prospects in baseball, lefty or not (he'd be No. 10 on our overall top pitching list if we had one). Armed with a fastball that touches 95 mph regularly, a plus slider that generates a ton of swings and misses, and a vastly improved changeup that also grades out as above average, Heaney has an outstanding repertoire and knows how to use it effectively. His stuff is good enough that if one pitch isn't working on a given day, he can still compete and win.

In the near future, Heaney's rough start to his big league career will be easily forgotten. When he settles in near the top of the Marlins rotation, right behind a healthy Jose Fernandez, it will be seen as a small bump in the road.

Mike Trout struggled when he first got up to the big leagues. Even Clayton Kershaw didn't dominate right out of the chute. Look for Heaney to learn lessons from his failures and establish himself as one of the better lefty starters in the National League in 2015.

Jonathan Mayo is a reporter for MLBPipeline.com and writes a blog, B3. Follow @JonathanMayoB3 on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.