Few pitchers pose the sort of philosophical inquiries that the Red Sox must wrestle in the case of Alfredo Aceves.

Who is he? What is he? What is his essence? Where is his value?

At times, the 29-year-old seems less like a pitcher than a case study for a Philosophy 101 class. Perhaps that is why he engages in such frequent mound conversations with catcher (and former Yale philosophy student) Ryan Lavarnway when the two are paired. After all, even Aceves speaks more in riddles than certainties about his role with the 2012 Red Sox.

After the right-hander continued a dominant spring by pitching four innings and allowing one run on three hits while striking out four and walking none, Aceves encapsulated his own ill-defined baseball existence.

“What are you looking for in Aceves?” Aceves asked reporters after his outing, returning a volley about the suggestions that he is too valuable as a reliever to shift to the rotation. “You say he’s valuable in the bullpen because he played in the past in the bullpen. Have you seen him as a starter? So, you will have to use the same word -- valuable -- for whatever role he has. So, he’s just valuable.”

That he is. But what kind of pitcher is he? In what capacity might he be most valuable to the Sox?

WHAT HE WAS LAST YEAR

Aceves was dominant as both a long man and setup man for the Red Sox last year, forging a 2.03 ERA out of the bullpen and logging 93 relief innings, most in the majors. He was a unique bullpen weapon, making 21 appearances of at least two innings (most in the majors) and 13 of at least three frames (most not only last year but tied for the most by any reliever this century).

At times, he performed as if a piggyback starter. When the Sox were getting few innings from their starters, Aceves was there to bail the team out for the “second half” of games, going two, three or even four-plus innings out of the bullpen. His outings were not starts, yet they were something other than the typical one-and-done that characterizes the modern world of relievers.

Some of the things that he did over the season were either underappreciated or borderline unfathomable. His 2.37 ERA against AL teams was the best by any pitcher to work at least 70 innings against the junior circuit. His 2.04 mark against the AL East was likewise the best in the majors (min. 50 innings).

Lefties couldn’t hit him (.190 average against). Righties (.216) fared little better.

By the end of the year, Aceves became a sort of duct tape out of the Sox bullpen, patching any hole, regardless of the size. In September alone, he threw a mind-boggling 25 innings out of the bullpen, performing at an extraordinary level.

His four starts yielded less impressive numbers, as he went 1-1 with a 5.14 ERA. That said, his stuff was better than those numbers suggested. He had two strong outings (at least five innings, one run), one outing that was impressive save for a brief and complete command blip (he gave up five walks in one inning to the Padres en route to a four-run yield in five innings) and another outing in which he was simply bad (5 1/3 innings, 6 earned runs).

Numbers aside, his four-pitch mix and ability to turn over a lineup out of the bullpen certainly looked like the attributes of a starter. That being the case, by the end of the season, David Ortiz openly questioned why he wasn't in the rotation.

At the time, Red Sox manager Terry Francona felt at the time that doing so might be an exercise in robbing Peter to pay Paul, something that was further underscored when Aceves handled a monstrous workload while pitching the final four games of the season.

Aceves did not have a specific role, instead allowing his workload to expand and contract like an accordion to bridge the Sox’ needs. While his job description seemed, in some ways, to be less significant than those of the closer or setup man, in other ways, it was even more significant. He may not have had the titles typically conferred upon pitchers who are pegged to the eighth or nine innings, but he operated, in some respects, like a relief ace who could deliver whatever outs the Sox needed.

Indeed, on a couple of occasions, multiple Sox decision-makers opined that a case could be made for Aceves as the most valuable reliever in the American League.

WHAT HE HAS BEEN THIS SPRING

Aceves entered camp prepared to compete for a job in the rotation, and to date, he’s performed as well as any starter the Sox have. In his three Grapefruit League games, Aceves has allowed one run in nine innings, striking out eight and walking none. He’s been carving the strike zone with his full pitch mix (fastball, cutter, curve, change), showing the diverse arsenal necessary to handle righties and lefties and to present opposing hitters with different looks to unbalance them through at least a second time through the order.

He’s made the responsibility he’s been given this spring look incredibly natural. At one point, his outing prompted manager Bobby Valentine to suggest that it looked like the right-hander had a day at the beach.

That said, almost every time that Valentine has been asked about the right-hander, he’s described him as being an outstanding “pitcher,” rather than talking about him in terms of starting or the bullpen.

Of course, his four starts last year were not dominant. However, if he is penalized for those, then he should also perhaps get credit for the four stars he made in 2008, when he was 1-0 with a 2.74 ERA for the Yankees.

WHAT’S MORE VALUABLE?

Aceves has been an enormously successful reliever at the big league level. He looks like he also could be a successful starter. But as Aceves himself suggested, no one knows how valuable he could be as a starter.

(Interestingly, the same is true of Daniel Bard, yet seemingly no one has asked the same questions of Bard’s value as a reliever vs. starter that are being asked of Aceves. Unquestionably, Bard’s electric arm would seem to present the greatest long-term upside to the Sox. That said, a) Aceves has more experience as a starter, making him something less of an unknown; b) the Sox likely would be more comfortable turning loose Aceves without innings restrictions than Bard based on past workloads, both in 2011 and in their careers; and c) while Aceves may lack Bard’s raw stuff, there is something of a right-handed C.J. Wilson-ish-ness about him, given his diverse array, his mound sense and his eccentricities.

That doesn’t mean that Aceves should start over Bard, but the fact that one is viewed as a near lock for the rotation and the other is not is simply intriguing.)

During the offseason, a couple of executives were queried about the relative value of a starter and closer. While Aceves has not been asked to close, his stature as a pitcher with tremendous value in a flexible bullpen role would still seem to make their answers germane.

Rangers Assistant GM Thad Levine, whose team has been transformed by the conversion of Wilson (2010), Alexi Ogando (2011) and potentially Neftali Feliz (2012) from the bullpen to the rotation, offered the following rough equation.

“It’s not formulaic. We sort of look at it as, in the regular season, a No. 1 or No. 2 starter is more valuable than a closer. Once you get to a No. 3, then you start I think questioning, depending on the caliber of how good the closer was,” said Levine during the offseason. “So for us, you hope when you make these transitions, you’re taking a guy who was a very accomplished closer. You’re hoping he has a chance to be a No. 2 starter. It’s not going to happen overnight. If he’s going to be a No. 3, then it’s about a break-even. If it’s less than that, then you probably should have kept him in the bullpen.”

One NL talent evaluator largely conferred with Levine’s assessment in the context of Bard's conversion.

“Unscientifically, I think a solid number three starter is more important than an above average closer,” he said, prior to the Sox' trade for Andrew Bailey. “So if Bard is, say, a No. 4 type -- roughly a 4+ ERA with some bulk innings -- he would be better served as a closer. If he is better than that, the experiment works.”

As for Aceves specifically, pitching coach Bob McClure recently suggested that, all things being equal, he looks like a pitcher who would be more valuable in the rotation than the bullpen.

“Alfredo, from what I’ve seen, may be one of our best pitchers,” said McClure. “I’m not talking about throwers. I’m not talking about stuff. But from a pitching standpoint, he’s very advanced as far as knowing what to do and when to do it and commanding a baseball at all different speeds.

“You know, he’s someone we have to really seriously look at as a possible guy in that starting rotation,” he continued. “To me, you win with starting pitching. Is it nice to have a guy like him in the pen? Sure it would [be]. It would be nicer to have a guy like him starting and a guy like him in the bullpen. But shoot, on every fifth day, you’ve got a guy who can pitch like that, go seven innings, eight innings, that can pitch every day, that’s nice to have.

“Unfortunately, and it happens to a lot of guys, it happened to myself as well. When I came up, I was a starter and they put me in the pen. You do OK and the next thing you know, you’re still in the bullpen and you’ve been wanting to start for two or three years. He’s in that boat. He’s done so well that everyone looks at him like, well, shoot, he’s so valuable there but I don’t know what’s more valuable than starting pitching, other than maybe a closer.

“I think Texas has shown that, to have five good starters, so you’re not keeping your fingers crossed, is this guy going to throw strikes today? If you’ve got five solid guys with a chance to win every single day, to me, that’s just more important.”

Even so, replacing Aceves in the bullpen would be no small task. Consider the idea that he delivered 20 more relief innings than Bard and nearly 30 more than Jonathan Papelbon -- not to mention offering four spot starts on top of that -- and one gets a sense of just how valuable Aceves was as a reliever. He worked, in some respects, time and a half in the bullpen. If there are concerns about the Sox’ relief  depth, then Aceves represents a potentially significant bullpen security blanket.

WHAT WILL THE RED SOX DO?

No determination has been made to this point. Aceves will make his next start in a minor league game on normal rest. For the Sox, there will ultimately be a number of questions to sort through, such as:

-- How valuable do they believe Aceves can be to a rotation? Is he capable of performing at the level of a No. 3 starter? Better? Worse?

-- How many innings do the Sox think he could take?

-- What is the short-term opportunity cost to the rotation? Do they feel that they would be able to have a pitcher of similar talents for the rotation if Aceves is back in the bullpen?

-- What is the short-term opportunity cost for the bullpen? Do the Sox have pitchers to replace Aceves if he’s in the rotation?

-- What are the long-term implications to the organization of putting Aceves in the rotation? If the team wants to maximize its long-term assets, would it be better off putting someone like Doubront (who has six years of controllable service time remaining) or Bard (who has four years before he’s free agent eligible) in the rotation, rather than Aceves (who has three years under team control)?

-- How valuable is he in the bullpen? Is he more or less valuable than a closer? A setup man?

To this point, there are more questions than answers with Aceves. He remains in his spring-long state of limbo, someone who projects as a key component of the pitching staff, but who remains enmeshed in philosophical dilemmas and uncertainties.