Many factors contributed to Boston’s 2013 World Series win. Two of the most notable included the Red Sox replacing Bobby Valentine with the far less divisive John Farrell, and pulling off one of the smartest offseason shopping sprees in years, paying Shane Victorino, Mike Napoli, Koji Uehara, and Mike Carp just slightly more than Vernon Wells’s annual salary.

The biggest reason for Boston’s worst-to-first season, however, was that the players who failed miserably in 2012 were amazing in 2013. David Ortiz, Jacoby Ellsbury, Dustin Pedroia, Jon Lester, Clay Buchholz, and John Lackey went from off years, lousy years, or entirely missed years to huge performances during the team’s ride to rings. Everything that could have gone wrong two years ago did, but then everything that could have gone right last year did, too.

Unless you’re one of my 681 Red Sox–loving bosses, though, you’re probably ready to move on to the coming season. So what can Boston’s 2012-13 turnaround tell us about 2014? Which teams suffered last season because of underachieving players but look poised to bounce back in a big way like the Sox just did?

I have some theories! Five teams fielded multiple players who dramatically underperformed last year, making those ballclubs prime candidates for some positive regression in 2014. And before you ask: Yes, you can construct a decent list of fantasy baseball sleepers and over/under candidates from our all-regression squad members. Starting with the …

Chicago Cubs

2013 record: 66-96

2013 Pythagorean record: 71-91

Starlin Castro could be the poster child for this exercise. When he signed a seven-year, $60 million contract on August 28, 2012, it looked like an excellent deal for the Cubs. They’d just locked up a player at the incredibly tough-to-fill shortstop position through the rest of his twenties, buying out as many as four post–free agency seasons. From 2010 to 2012, Castro’s first three big league seasons, only five other shortstops (Troy Tulowitzki, Jose Reyes, Hanley Ramirez, Asdrubal Cabrera, and Derek Jeter) were more productive offensively on a park-adjusted basis. Castro was just 22 at the time, and he’d posted a .297/.336/.425 line over his first three seasons. While not all players develop at the same rate, Castro looked poised to improve over the course of the deal if he joined the majority of baseball players who peak in their mid-to-late twenties.

That’s what makes me doubt that Castro’s disastrous 2013 season has much predictive value. It’s very rare for a player with Castro’s ability to fizzle out at this young of an age absent a catastrophic injury (Tony Conigliaro) or a major substance abuse problem (Ellis Valentine). Neither of those things happened to Castro, so the smart money says his .245/.284/.347 2013 campaign was a massive aberration and he should return to his previous offensive norms in 2014.

That alone would be enough to make the Cubs three wins better this coming season, but Castro will have company on the regression train. A big plunge in Anthony Rizzo’s batting average on balls in play last year (from .310 in 2012 to .258 in 2013) belied a big improvement in his walk rate. Rizzo is just 24 years old himself, and he figures to put up significantly better numbers in 2014, partly thanks to some of that positive regression, and partly thanks to normal development for a player who’ll be entering just his second full big league season. While Darwin Barney is clearly in the lineup for his Gold Glove–caliber defense and not his weak bat, it’s hard to imagine him hitting like a pitcher again (.208/.266/.303), especially since he was another victim of bad batted-ball luck (.222 BABIP). Meanwhile, Jeff Samardzija’s ERA trend (2.97 in 2011, 3.81 in 2012, 4.34 in 2013) looks nothing like his fielding-independent numbers (3.66 FIP in 2011, 3.55 in 2012, 3.77 in 2013), which means his luck should improve this year. Ditto for Edwin Jackson, who was the second-unluckiest starting pitcher in the majors by one measure last season. Reshuffling the worst bullpen in the NL won’t hurt, either.

The Cubs likely won’t contend for the 2014 NL Central crown, but they could easily win 10 more games than they did in 2013.

Los Angeles Angels

2013 record: 78-84

2013 Pythagorean record: 81-81

To calculate Wins Above Replacement, FanGraphs and Baseball-Reference.com combine runs created on offense, runs saved on defense, and baserunning runs, then adjust those numbers against league and positional averages. I bring this up not to start a war on WAR, but to highlight the Offensive Runs category, specifically Albert Pujols’s history with that stat. In the first 10 years of his career (2001-10), Pujols led the majors in Offensive Runs created, with 609. This isn’t a commonly used stat, so without context it’s tough to grasp what that number means. Try this: The no. 2 hitter on the list is Barry Bonds, and he generated 23 percent fewer runs with his bat during that decade than Pujols did. Now jump ahead to 2013. Last season, Pujols generated exactly as many runs with his bat as Seth Smith did. No disrespect to Smith, but the Angels didn’t spend a quarter-billion dollars to get a hitter of that ilk.

Last year marked Pujols’s third consecutive seasonal decline, and even the biggest optimist would concede that the old Pujols who hit .330 with 90 extra-base hits a year isn’t coming back. Still, even within the context of an expected decline as Pujols progresses into his thirties, 2013 looks like a big, fat outlier. Pujols missed 63 games last year because of plantar fasciitis, an injury that plagued him from Opening Day, and a May knee injury didn’t help; even in the 99 games he played, Pujols was clearly hampered. Plantar fasciitis is an incredibly painful injury that can linger for months, even years absent proper rest, and baseball players don’t have the luxury of staying off their feet during the season. The four-plus months between the end of the regular season and the start of spring training should afford Pujols enough time to heal, however. He’s not going to perform like he did from 2001 to 2010, but if a healthy Pujols simply returns to his 2012 levels of production, he’d give the Angels a three-win swing.

Now add in some positive regression for Josh Hamilton, who was bound to suffer after going from hitter-friendly Arlington to pitcher-friendly Anaheim but whose dip from .285/.354/.577 to .250/.307/.432 screams flukish off year. Figure also that David Freese will be a solid upgrade over Alberto Callaspo and his band of replacement-level men. Sprinkle in a couple of nifty starting pitcher pickups in Hector Santiago and, if healthy and motivated, Tyler Skaggs, and the Angels bring ample upside.

Plus, while it’s merely speculation at this point, the rumor mill has the Angels going after Masahiro Tanaka or another quality starting pitcher before hot stove shopping concludes. If they’re successful on that front, start discussing the Angels as a wild-card contender.

Washington Nationals

2013 record: 86-76

2013 Pythagorean record: 84-78

It might seem a bit weird to suggest a rebound season for a team that won 86 games, but it’s hard to express just how much of a disaster catcher and second base were for the Nats through much of last season. After recovering from ACL surgery, Wilson Ramos suffered a hamstring injury that torpedoed his season, limiting him to just 78 games. His catching counterpart, Kurt Suzuki, inexplicably hit rock bottom in 2013, batting just .222/.283/.310 in 79 games with the Nats.

Danny Espinosa, Washington’s Opening Day second baseman, was coming off a 2011-12 stretch in which he batted just .242 but still averaged 19 homers and 33 doubles a year. Espinosa hit like a poor man’s Carlos Zambrano in 2013, eventually losing his job. Steve Lombardozzi got 307 plate appearances while subbing at second and elsewhere, about 297 more than he should have. The Nationals eventually found a new everyday second baseman in Anthony Rendon, who hit much better than Espinosa but not quickly enough to help save their season.

A full year of Ramos behind the plate and Rendon at second could be worth three or more wins to Washington in 2014. Sub in Doug Fister for Dan Haren, who had just a 4.67 ERA and 4.09 FIP last year, and figure that the bullpen will blow fewer than 21 save chances in 2014, and last preseason’s hugely optimistic forecasts for the Nats might come to fruition one year late.

Toronto Blue Jays

2013 record: 74-88

2013 Pythagorean record: 77-85

We all overrated the Blue Jays last year; let’s start there. Josh Johnson might’ve been very good in 2012, but his injury history should have made us wonder if he could again carry the load for 30-plus starts. Same goes for Brandon Morrow. R.A. Dickey might’ve been the defending Cy Young winner, but the knuckleball can be a fickle beast, and tossing Dickey into the AL East lion’s den was always going to be a risk. The disappointing seasons turned in by those three pitchers alone would have knocked several wins off the lofty 2013 projections most had for Toronto, and that’s before we get to the many other mishaps that befell the Jays last year.

Almost by default, the Jays figure to trot out a much improved rotation in 2014. Many able-bodied humans with half-functioning arms could manage a better ERA than the 6.20 mark Johnson posted last year before the Jays let him walk and sign with San Diego. Morrow is still a Jay, meanwhile, and he’s still very much a health risk, having made just 31 combined starts over the past two years; however, his prior history didn’t include anything remotely as bad as the 5.63 ERA he posted last year.

While the leaky pitching staff rightly shouldered most of the blame for Toronto’s disappointing season, the Jays also suffered multiple lineup setbacks. Colby Rasmus’s breakout season was undermined by 44 games lost to injury. Jose Bautista maintained his status as one of the AL’s top sluggers, but he, too, missed 44 games. Brett Lawrie’s track record suggests he’ll do better than .254/.315/.397 when he’s not missing 55 games. Jose Reyes carries an extensive history of injuries, but his 93 games played in 2013 marked his second-lowest total since becoming a full-time player in 2005. J.P. Arencibia, Melky Cabrera, Emilio Bonifacio, and Maicer Izturis were so bad that the mere act of deleting them from the roster (Arencibia and Bonifacio), relegating them to the bench (Izturis), or putting them on a very short leash if they stink again (Cabrera) portends a gigantic improvement.

Look for the Jays, who’ve had a quiet offseason so far, to make a run at Ervin Santana or Ubaldo Jimenez to bolster the rotation. Even if the team stops there, Toronto could make a big leap in 2014 simply by having even modest luck. The 2013 Jays are the best equivalent of the “everything that could go wrong did go wrong” 2012 Red Sox.

Milwaukee Brewers

2013 record: 74-88

2013 Pythagorean record: 76-86

This one’s simple: Ryan Braun. While we’re bound to remember the 65-game PED suspension, it’s easy to forget that Braun was hampered by a hand injury before his punishment came down, and he was often out of the lineup or playing hurt. It’s tough to say for sure exactly how good Braun will be in 2014, assuming he’d been juicing for some time before his suspension, and assuming he’ll be completely PED-free upon his return; we simply don’t know enough about the specific effects of specific performance-enhancing drugs on specific players to say one way or another. But if Braun’s anywhere close to the player he was before, he’ll give the Brewers at least four or five more wins right away.

Milwaukee’s other positive-regression candidates include Aramis Ramirez, who has always been injury-prone but has rarely missed as much time (70 games) as he did in 2013; whomever the Brewers put at first base to replace new Mariner Corey Hart, who was projected to start last season but missed the whole year, and whose replacements were collectively terrible; the bullpen, after a group of relievers with decent-to-good track records suddenly struggled terribly in 2013; and Yovani Gallardo, whose fastball velocity dropped, portending his worst numbers in five years.

Like the Cubs, the Brewers have too many roster holes and too much quality competition to project as real threats in the NL Central. But Milwaukee won 83 games in 2012 and just 74 in 2013 despite carrying a nearly identical roster and getting big contributions from a terrific up-the-middle core led by Carlos Gomez, Jean Segura, and Jonathan Lucroy. Even if those three 2013 stars decline a bit, the Brewers could easily return to .500 or better in 2014.

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An earlier version of this column has been updated to clarify that Melky Cabrera is still on the Toronto roster.