Projecting best- and worst-case Red Sox rookie seasons for 2014

Projecting baseball performances is difficult, but projecting what prospects are going to do once placed in the major leagues is even more problematic. Gauging just how little or how much the transition to facing the best hitting or pitching in the world will strike a blow to a prospects' gaudy minor-league numbers is no easy task, but there are ways of finding a reasonable range of outcomes.

Baseball Prospectus has finally released my personal favorite part of their PECOTA projection system: the percentile forecasts. These give a best-case, worst-case, and everything in-between forecast for players for the upcoming year. When dealing with prospects, who are inherently all over the place, it's a valuable tool for forming reasonable expectations flanked by measured optimism and, where appropriate, pessimism.

We'll look at five Red Sox prospects who could play significant roles with Boston in 2014, and do so through the lens of PECOTA's percentile projections. Rather than list out each percentile, 10th through 90th (where 90th is best-case, 10th is worst-case), we'll check out the extremes and the middle ground they've created to see what we have to look forward to with Boston's youth.

Xander Bogaerts

You might have heard of this Bogaerts kid at some point. He's the greatest prospect the Red Sox have produced since Hanley Ramirez, but unlike Hanley, Xander is going to play in Boston. He's their starting shortstop, and while he picked up some playing time at the end of 2013, no one has seen what he's capable of on the major-league stage yet, at least not fully. He'll be just 21 this year, in his first full-season campaign in the bigs, leaving plenty of questions about what his performance could look like.

PECOTA forecasts Bogaerts for a mid-range projection of .265/.327/.433, good for a well above-average .277 True Average (the average shortstop TAv a year ago was .248) that comes close to replicating Stephen Drew's .282 mark from Boston's 2013. That's good and all, especially at Xander's youthful age, but PECOTA also believes he's capable of a much more commanding entrance to the majors, forecasting him for a 90th percentile of .306/.373/.500, for a TAv of .315.

For the sake of context, Troy Tulowitzki led all shortstops (minimum 450 plate appearances) in True Average a year ago, at .306. Again, PECOTA isn't saying that this is absolutely what will happen, that Bogaerts will be the top offensive shortstop in baseball as a 21-year-old rookie. It's just saying the possibility is indeed there. I'll take it.

By the same token, PECOTA isn't suggesting that Bogaerts will totally flop in his first extended big-league stint when it projects a .217/.272/.353 10th percentile forecast. The possibility exists that he cruelly disappoints us all, though. Baseball has been known to do that, time and again, regardless of how talented a player looks to be.

Jackie Bradley Jr.

Bradley might not be the Opening Day center fielder, not if Grady Sizemore is healthy and looking like his old self. Let's say he is, though, and see what PECOTA has to say about the future of center in Boston in the present. His mid-range projection is solid enough, at .257/.346/.405 -- with his glove, that's a pretty useful player, as his above-average wins projection says. He could be much better than that, however, if he learns to hit fastballs low-and-in, and stops trying to hit for power when he should be looking to secure base hits and better pitches to drive. Were he to do all that, we might see something akin to his 90th percentile line of .299/.395/.472.

Now, I have to say that, as much as I adore the idea of Bradley Jr. in center field in Boston for the next six-to-seven years, I'd be surprised if he ever put together a season like that. I like his bat plenty, but this might be one of those areas where projection systems have a thing or two to learn from scouts. Bradley's 10th percentile projection seems more believable than his 90th, at .208/.286/.327. Again, I'm not expecting that -- his mid-range projection looks like it's on the nose here, if you're making me choose -- but it's more realistic than Bradley being Bogaerts' offensive equal. If Bradley puts together a season like that 90th percentile in his career, I doubt it's in 2014.

Allen Webster

If Webster can figure some things out at Triple-A Pawtucket, and there is an injury or two in the rotation in Boston, he might find himself back in the majors, starting once more. PECOTA hates that idea, as you can imagine -- I did say he had to figure some things out at Triple-A before coming back up -- projecting him to a 5.13 ERA, an average seven strikeouts per nine, and a 1.7 strikeout-to-walk ratio. Things are happier in the 90th percentile, with Webster posting a 3.96 ERA and getting his K/BB over two, but they still aren't great. That's fine, though, and expected: Webster still has a lot to prove, and it's good enough to see PECOTA hasn't given up on the idea of his being useful. A 3.96 ERA from a rookie in the AL East is lovely.

Given what his mid-range projection looks like, you can probably guess what PECOTA sees for Webster at the 10th percentile. It's best we move on.

Brandon Workman

PECOTA sees Workman primarily as a reliever, which colors his forecasts a bit. Workman will most-likely start for the Red Sox if he shows up in the majors, as he's the sixth starter who will arrive on the scene when a pitcher hits the disabled list, while Chris Capuano is the spot guy there to absorb four-to-five innings on nights when a pitcher is scratched, but not disabled.

Photo credit: Dilip Vishwanat

Workman is projected for just a 4.45 ERA at the mid-range, which would be a half-run improvement on 2013's 4.96 mark in the majors. At the 10th percentile, PECOTA sees Workman as a sub-replacement arm -- this is the kind of thing that could happen to the big righty, should he not have his fastball command where it needs to be, as often as it needs to be. At the 90th percentile, however, a quality arm is projected, one who would put up a win above replacement in a season of relief, posting a 3.34 ERA in 34 games, six of them starts. That's a little optimistic for me in terms of starting -- he's more of a league-average arm capable of eating innings -- but with the emphasis on relief in this projection, I get where the ERA is coming from.

Bryce Brentz

Brentz will only see major-league time if it's September or something has gone horribly wrong over the summer, a la 2010's outfield that resulted in both Josh Reddick and Ryan Kalish getting involved. Were he to show, up, though, PECOTA sees the righty batting .253/.295/.425, showing off some power, but also failing to get on base. You probably could have guessed yourself, but PECOTA also sees Brentz striking out with alarming regularity: 129 punch outs in 456 plate appearances, or 28 percent of the time.

At the 10th percentile, Brentz is forecasted to whiff over 30 percent of the time, with a batting average so low that his power cannot save him, and so devoid of walks that he's about 20 points below replacement level offensively, by True Average's reckoning. Things are cheerier on the flip side, at least, with Brentz forecasted for a .292/.338/.493 showing. The fact that the most optimistic of optimistic lines sees him producing a .338 on-base percentage is pretty telling about where he is in his development, though.