PHILADELPHIA -- The pitch that brought R.A. Dickey to prominence, the knuckleball, is a serviceable metaphor for the career paths of many of its practitioners, including Dickey himself.

Watch the pitch, uniquely vulnerable to conditions, dip, dive and drop in concert with Tim Wakefield's Baseball-Reference.com page. Dip with him to a 2.15 ERA in 1992, surge upward to a 5.61 ERA in 1993, back down to the 2.95 in 1995. He was a 33-year-old pitcher with a 5.48 ERA in 2000, the kind of line and age that usually means the end is near. Wakefield pitched another 11 seasons, contributing to a pair of World Series championships in Boston.

You can find similar season-to-season sways from other knuckleballers, people like Phil Niekro and Charlie Hough. And Dickey, who'd been pretty consistent, actually, in three seasons with the Mets from 2010 through 2012, had it happen to him last season. That 2.73 ERA in 2012, part of his Cy Young and consciousness-raising season, elevated to 4.21 in 2013 after the Toronto Blue Jays acquired him. Even adjusting for year, park and league, Dickey's ERA+ dropped from 139 in 2012 to 98 in 2013.

Dickey entered the visitors' clubhouse at Citizens Bank Park Tuesday afternoon looking about as I remembered him from his three seasons with the Mets: Unruly mop of hair above a shaggy beard, a mane irregularly framing his face while he shares complicated thoughts on whatever subject is under discussion. It's like talking to an elite athlete shaggy dog who's an English professor.

"You know, I think there are a number of reasons for that," Dickey said about the large deviations in the careers of knuckleball pitchers generally. "I think the climate does play a part. And so, being comfortable with where you are, and trying to figure out, dynamically, what that pitch is going to do in response to the climate is an issue that a knuckleballer has to take into consideration."

Dickey, unprompted, pivoted from this answer generally to an explanation of his 2013 season.

"Pitching in Toronto, where there's less humidity, and the dome is open one day, closed the next, that kind of thing, I think was -- I was also nursing an injury last year, trying to figure out that release point. All those thing compounded, resulted in more walks, I feel like. This year, it's a similar feel. I'm just trying to figure out when the weather's gonna warm up a little bit. I always feel like I do better when the weather's warmer outside."

With that, Dickey returned to the larger brotherhood.

"The pitch is vulnerable to more parameters that can influence it than a conventional pitcher would. It's just the way it is."

All of what Dickey discussed in that response, and more, comes into play when evaluating what Dickey is as a pitcher at present, and what he will be going forward.

The stakes are pretty high for the Toronto Blue Jays. Their GM, Alex Anthopoulos, sent a huge package of prospects to the Mets during the 2012 offseason to acquire Dickey. Noah Syndergaard, now considered one of the best pitching prospects in baseball, Travis d'Arnaud, now New York's starting catcher, and others went to New York for the chance to add two years, $24 million, and a team option for 2016 at the same annual price to Dickey's contract.

Viewed through the prism of the trade itself, any time Dickey is less than the Cy Young Award winner from 2012, it's hard to justify that much in young talent for the deal. The deal was made so Toronto could contend immediately, which hasn't happened. The deal, and Dickey's performance, will also be judged to a large extent by how d'Arnaud and Syndergaard perform. None of that is particularly fair to Dickey, nor is it anything Dickey can control.

"As for last year, I think for me, in the AL East, it wasn't a terrible year," Dickey said. "It definitely wasn't a Cy Young year. But I think if I hadn't won the Cy Young the year before, I bet it would be considered in a whole different way than it was considered."

Dickey, in isolation, represents a puzzle. By conventional aging curves, betting on that Cy Young standard for Dickey, entering his age-38 season last year, 39 now, wouldn't seem to make much sense.

But while knuckleball pitchers can suffer from downward deviations from typical career paths, the same is true in the opposite direction. The pitch can take irregular turns for the better, a ball reentering the strike zone unexpectedly. And just like the pitch, knuckleballers often take longer to get to the end of their journeys, pitching deep into their 40s.

Witness Phil Niekro, with his 12 200-inning seasons from age 35 on, four All Star game appearances, three top-six Cy Young Award vote finishes. Witness Hough and his run of six straight seasons of 110 ERA+ or better from ages 35-40, leading the league in innings pitched at age 39.

According to Anthopoulos, the work and the potential for excellence is plenty to justify the deal.

"The age is kind of irrelevant for him," Anthopoulos said during an interview in the visiting dugout Tuesday. "One, he's a great athlete. He takes care of himself. It's not a surprise he won the Gold Glove. But no, you look at historically, guys who threw that pitch, it doesn't seem to be nearly the factor it is for guys with a regular mix.

"He really turned it on in the second half of last year. He's had a few outings this year where he's just been dominant against certain teams. He's been up and down, but we think R.A.'s gonna have a great year for us. He's gonna log a ton of innings, won 14 games for us on a last-place club. And he can get on a roll, really get on a tear at any time."

dickey on deck
Dickey waits on deck in a game against the Pirates in Pittsburgh. (Getty Images)

Searching for commonalities in such a small group of knuckleball pitchers makes figuring out what R.A. Dickey is, and can be, difficult. Dickey's 2012 separated him even from his fellow knuckleballers, with the speed of his primary pitch reaching an average of 78 miles per hour. Not only that, but his secondary pitches, a collection of two-seam and four-seam fastballs, averaged 84 and 85 miles per hour, respectively.

His average velocity on the knuckleball dropped to 76.18 miles per hour last season, and neither of his fastballs reached 83 miles per hour on average. There are a few issues within those drops. One is that any decline in velocity on the fastball makes it easier for hitters to adjust to it. The same is true, incidentally, on a knuckleball. He's getting fewer swings and misses as a result, dropping his strikeout rate considerably from his 2012 peak to date. Moreover, Dickey believes the reduction in knuckleball velocity affects his ability to throw the pitch for strikes.

"The speed I feel most comfortable with, throwing a strike, is that 76, 77 mile per hour knuckleball," Dickey said. "That's the one I feel if that can be the mean, especially for the year, then I feel that can be successful. It's when that starts to creep down that I have trouble throwing it for strikes, because the release point's different. If you're throwing a 72 mile per hour knuckleball, it's a little bit different release point. Last year, when I was hurt, I threw a lot of 72 mile per hour ones, because I just couldn't generate the arm speed.

"It also gives it more time to move. Because if you're five, six, 10 miles per hour slower, then it's that much more time it has to move out of the strike zone."

If there's been a single constant in Dickey's time as a knuckeballing starter, dating back to 2010, it's a slow start followed by an improved finish. He didn't reach the big leagues for the Mets until the weather turned warmer in 2010. In 2011, his ERA was 5.08 in his first nine starts, 2.69 the rest of the way. Even in his magical 2012, his April ERA was 4.45. The results were good in a May 6 start, eight innings of one-run ball, but he walked four and struck out four. May 12, he failed to strike out a batter. Then he went on a tear, pitching to a 2.52 ERA over his remaining 27 games, and striking out more than a batter per inning.

"I was winning games, but some of them weren't very pretty," Dickey said of his 2012 season. "And once we got into mid-May, I felt like the weather was warming up, the humidity was better, all those things kind of impact the movement of the pitch."

His 2013 followed a similar trajectory, though his start was a bit worse, his second-half improvement came a bit later, and it wasn't quite at the level of his revelatory 2012. His velocity, even in just the second half of 2013, didn't approach 2012 on his knuckleball or fastballs. He didn't throw his knuckleball, or his two-seamer or four-seamer for strikes as often in 2013 as he did in 2012. So far, in 2014, he's throwing all his pitches for strikes even less, failing to crack 40 percent strikes on any of them. Through nine starts, 26 percent of his knuckleballs have been strikes. Thirty-eight percent were balls.

Dickey will be 40 in October. He throws an unconventional pitch. But that doesn't make him, or his arm, or the pitch itself magically immune to aging.

Over his last three starts, though, command of his fastballs, though not velocity, has returned to 2012 levels. He's still having trouble with the knuckleball, command-wise, but the fastball command alone has his strike percentage up, along with a jump in swings and misses. It was the strikeout rate, really, that made him a Cy Young pitcher in 2012.

Are the last three starts representative? Are the last seven? Is 2013? 2012? Will the next 20-plus starts, taking place in the warmer months, tell us who R.A. Dickey is as a pitcher, now and going forward?

Dickey is a voracious reader and writer. These days, he's carrying around the Best American Short Stories 2013, a collection of tales written by some of top-notch contemporary writers. There's short fiction from Junot Diaz, Lorrie Moore, George Saunders, Alice Munro and Steven Milhauser. They're all forever linked now, in this anthology, like Dickey's seasons. But extrapolating how Saunders will write from Diaz's story is an exercise in futility.

Accordingly, the narrative of Dickey's career looks less like a novel, and more like a series of short stories. Predicting the arc of them collectively would mean forcing Dickey's career into a form that doesn't suit it.

Dickey's first book came out in 2012. His children's book published earlier this month. And Dickey says he is at work on another book as well. But authoring his life, and particularly his baseball career, is more complicated.

"I really don't consider the arc much," Dickey said about the broader scope of his career, or where he sees himself at within it. "I kind of just try to become infatuated with the moment as much as possible. I feel, physically, like I could pitch another ten years if I wanted. But I think there are some extenuating circumstances in my own life that will reduce the number of years that I will play over what I could play. Wanting to be a father full-time, and a husband, things like that.

"But as far as the way I feel, I feel great. And I just try to remember the reason I had success in the first place, and that's to really engage the moment as fully as possible. And I don't go too much -- I don't project out to where will I be in three or four years, to distract from where I'll be in the present. But I feel like, 200 innings, and averaging a three-and-a-half, 4 ERA, is a pretty good year for most guys. And if you can do that for a number of years, then you should always have a job. So I feel like I'll be able to do that for a while. But as far as how long I can pitch, who knows?"