PORTLAND – Followers of the Portland Sea Dogs and the Red Sox minor- league system have seen many a pitching prospect step onto the Hadlock Field mound and deliver.

Jonathan Papelbon, Jon Lester and Clay Buchholz come to mind. Then there are names like Justin Masterson, Michael Bowden, Junichi Tazawa and, this year, Felix Doubront.

But what are the Red Sox to make of Casey Kelly? If you look only at the numbers, you won’t think much.

After 16 starts, Kelly is 1-4 with a 5.45 ERA. In his last four games, he’s allowed 18 earned runs in 19 1/3 innings.

What were the Red Sox thinking when they drafted Kelly in the first round in 2008, then handed him a $3 million signing bonus?

Well, the Red Sox thought there were getting a prized prospect.

And they still do.

“Casey Kelly is showing really good stuff,” Sea Dogs pitching coach Bob Kipper said.

Kipper isn’t just saying nice things about one of his pitchers. At times, Kelly, 20, demonstrates talent beyond his age, and definitely beyond his experience. His fastball reaches 94 mph and paints both corners of the plate. The curveball is deadly and the change-up looks fine.

So why aren’t the numbers better?

“I’m actually learning how to pitch,” Kelly said.

And he’s right. No Red Sox pitcher in recent memory has arrived in Double-A with less pitching experience.

Remember, Kelly is an exceptional athlete. The University of Tennessee recruited him as a quarterback. Other pro baseball teams looked at him as a shortstop. He batted .473 his senior year at Sarasota (Fla.) High in 2008.

Kelly didn’t see himself as a pitcher, although he was dominant. So when he wasn’t playing football (fall season and spring practice), he was mostly playing shortstop.

After he was drafted in the summer of 2008, Kelly played the infield in short-season Class A, first in the Gulf Coast League, then for Lowell.

In a unique arrangement in 2009, Kelly pitched the first half of the season for Class A Greenville, then advanced Class A Salem, then switched back to shortstop.

All told, Kelly pitched only 17 games last year — going 6-1 with a 1.12 ERA in Greenville, and 1-4 with a 3.09 ERA for Salem.

As a hitter, Kelly batted .219 (64 of 292). He might have improved as an everyday player if he concentrated only on that. But the Sox and Kelly figured his best potential was on the mound.

Instead of letting Kelly put up more good numbers this year in Class A, he was promoted to Portland — after only 95 innings of pro experience.

When Papelbon pitched here, he was 24 and had both college and 162 innings of pro pitching experience.

Lester, like Kelly, was drafted out of high school. But Lester was 21 when he came to Portland, having pitched 47 games in the lower levels.

Buchholz pitched briefly in college, then worked 160 innings in the lower levels before coming to Portland at 22.

Bowden was 19 when he came to Portland in 2007, but he already had pitched 165 innings in the pros.

And it took Bowden a while to come around in Double-A. His ERA was 4.28 in 2007, then improved to 2.33 in 2008.

Which brings us back to Kelly.

“Casey had half of a season of professional baseball under his belt at the lower levels,” Kipper said. “It’s a little different here (Double-A).

“(Batters) understand the strike zone better. They’re going to work (at-bats), and that’s how it is in the big leagues.

“So Casey Kelly will work through that. Being able to deliver the complete performance — we haven’t seen that often enough.

“But I just think that’s part of the development. It can’t be about the numbers. That’s what I tell all the guys.”

But that doesn’t make it easy to take sometimes.

Kelly allowed six runs over 51/3 innings Tuesday night, including a three-run homer on a hanging curveball.

Afterward he sat in front of his locker, his million-dollar arm wrapped in ice, his eyes staring downward.

Wednesday, Kelly was bouncing around Hadlock, smiling and chatting with teammates during batting practice.

“It’s frustrating when you have a couple of pitches that you would want to change, and it affects your outing,” Kelly said. “But for the most part, I just kind of look at it the next day and examine what went wrong and what I can change for next time.

“Just figure out ways how to get better for my next start.”

Kelly’s maturity and poise is a reason the Red Sox felt comfortable starting him in Double-A this season. Kelly is the son of a minor-league manager, Pat Kelly. Casey Kelly grew up around minor-leagues clubhouses. He understands what the minors are about.

“If you have a 1.00 ERA in the minor leagues, it really doesn’t matter much,” Kelly said. “A lot of times last year, I had so much success that I really didn’t have to deal with failure.

“I’d much rather deal with failure here than in the big leagues.”

And the failure hasn’t slowed Kelly from developing. He’s not trying to nibble around the plate with pitches — a la Daisuke Matsuzaka — trying to get hitters to chase.

For the most part, Kelly is throwing strikes, unafraid of the result.

“He’s relentless in his willingness to attack the strike zone and pitch to contact,” Kipper said.

Kelly also gets swings and misses. In 672/3 innings, he has 63 strikeouts and 28 walks.

In his last start, when he gave up six runs, Kelly struck out eight.

“He pounded the zone and went after guys,” Portland Manager Arnie Beyeler said. “He’s just a tough-luck guy right now.

“You’re gong to run into that with the young guys. They’re inconsistent. Things get a little quick on them and they struggle to minimize that one big inning.”

So when Kelly makes his next start this afternoon, he may give up some runs, maybe a big inning.

But Kelly is learning. The numbers will get better, the outings more consistent.

Eventually, he will pitch in Fenway Park. Then Hadlock fans can boast that they knew all along that the kid was special.

Sometimes you have to ignore the numbers.

Staff Writer Kevin Thomas can be reached at 791-6411 or:

[email protected]