Teams don’t always have to make a major move in order to improve over the winter. Sometimes merely subtracting someone who played poorly can affect our expectations for a club. Occasionally, a series of seemingly minor moves can make a major cumulative impact. And at other times, there’s an obvious in-house fix for a roster’s flaws in the form of a player returning from an injury, being promoted from the minors, or switching to a position where he’ll be of more use. The Rays went from last place in 2007 to first place in 2008 without acquiring an outside player more accomplished than Troy Percival. Some off-season overhauls don’t start making headlines until the regular season is well under way.

Still, the moves that make us dream about how good a given team can be when players report to spring training tend to be the ones involving established talents. When we’ve already seen what a player can do, it’s easy to picture him doing it again in a different uniform. Naturally, the more a team struggled at the new player’s position last year, the more exciting the upgrade. But it’s easy to get carried away and overstate the improvement. Assessing the impact of a high-profile player addition requires more than a little imagination and mental arithmetic.

Using the rate statistics predicted by PECOTA, Baseball Prospectus’ proprietary projection system, and the human-generated playing-time estimates contained in our depth charts, we’ve come up with an estimate of what each team can expect from each position in 2012. By comparing those estimates to the production we know those teams got from the same positions last season, we can pinpoint the biggest positional improvements according to BP’s total value metric, Wins Above Replacement Player (WARP). The following seven positions improved by an estimated two wins or more this winter thanks to a trade or free-agent signing.

Angels, First Base (4.9 WARP improvement)
Angels first basemen weren’t bad last season. Mark Trumbo got the bulk of the at-bats, hitting 29 home runs and finishing as the runner-up for the Rookie of the Year award. Howie Kendrick hit .417/.440/.604 in 50 plate appearances at the position. Altogether, Angels first basemen produced 2.4 WARP, roughly an average total. In general, it’s tough to improve on “average” by leaps and bounds—it’s easier to go from hopeless to average than from average to elite—and the biggest gains are often achieved by swapping out a sub-replacement player for a more dependable mid-level option. There are exceptions to this rule, but they don’t come cheap.

Albert Pujols is one such expensive exception. The Angels spent $240 million on the winter’s most coveted free agent, and PECOTA projects that they’ll get more than their money’s worth, at least in 2012. Before his final year in St. Louis, Pujols hadn’t been worth less than 7.8 WARP in a season since 2002, and despite his slow start and subsequent wrist fracture, he was still a six-win player last season. PECOTA expects him to approach the eight-win mark again in Anaheim. That means the Angels can expect to add about five wins at first base, not to mention another 1-2 trickle-down wins at DH.

Mariners, Designated Hitter (3.9 WARP improvement)
The Mariners tried 14 players at DH last season, none of whom stuck or succeeded there for long. The result was a collective .225/.316/.332 performance, led by Jack Cust at .213/.346/.330. Sadly, that was an improvement over the previous season, when Milton Bradley and Ken Griffey Jr. played their way out of baseball and Mariners DHs hit a combined .194/.269/.340. Seattle has struggled to find someone who can hit to be their designated hitter since Edgar Martinez’s last productive season in 2003.

Michael Pineda may have been a high price to pay for someone who probably can’t play the field, but in former Yankees prospect Jesus Montero, the Mariners may have gotten themselves another Edgar for the foreseeable future. PECOTA isn’t expecting miracles from Montero in his first full season, but a .290 True Average (TAv) and 24 homers, plus some solid supplemental work from Mike Carp, would make for a substantial improvement over the losers of the past several seasons.

Brewers, Third Base (3.9 WARP improvement)
Brewers third baseman Casey McGehee was one of the least-productive regulars in the majors last year, playing about a win below replacement level after two seasons of roughly average performance. Rather than hoping for him to rebound, the Brewers made McGehee the Pirates’ problem and brought in a name-brand third baseman to replace him.

Aramis Ramirez isn’t quite the player that his bat makes him out to be, since his work outside the batter’s box leaves a lot to be desired. His fielding and baserunning cost the Cubs two wins last season, making him more of a 2-3 win player than the 4-5 win force he’d be if he were even average away from the plate. However, he still represents nearly a four-win improvement over what McGehee gave Milwaukee last season, which should make up most of the deficit Prince Fielder’s departure opened up on the other side of the diamond.

Angels, Catcher (3.1 WARP improvement)
Jeff Mathis might be the worst hitter in baseball. Among batters who’ve made at least 1000 plate appearances since 2005, only Humberto Quintero has a lower TAv than Mathis’ .207. Even though Mathis is a fine fielder, everything we’ve learned about catcher defense suggests that his glove couldn’t make up for his historically bad bat. Mike Scioscia insisted on starting him anyway, and with Mike Napoli away, Mathis played more last year than he had in any season since 2008.

Angels GM Jerry Dipoto emphasized the importance of on-base percentage shortly after taking over last October, and he backed up his words by trading for Chris Iannetta a month later. The former Rockies catcher has walked in 13.9 percent of his career plate appearances, a higher rate than any Angels regular managed last season. He hasn’t hit as well away from Coors Field, but he still has a career .268 TAv, which means he’s been an above-average hitter (and a well above-average offensive catcher), even after adjusting for his home park.

Marlins, Shortstop (2.4 WARP improvement)
Here’s another case of a large contract leading to a correspondingly large on-field improvement. Marlins shortstops were worth close to two wins last season despite an injury-plagued and abbreviated campaign by Hanley Ramirez, but Miami signed a superstar in Jose Reyes this winter, so it should come as no surprise that we expect the infield to be much improved.

Since Reyes’ arrival will push Ramirez to third base, where the Marlins made do with Greg Dobbs for most of last season, the team’s greatest gains may come at the hot corner. Assuming Hanley stays healthy and happy and his bat rebounds, Miami might be almost eight wins better on the left side of the infield.

Padres, Left Field (2.4 WARP improvement)
Padres left fielders barely played above replacement level last season, as Ryan Ludwick struggled to a .249 TAv before being traded to Pittsburgh. Kyle Blanks did better, but Josh Byrnes solidified the position further by trading for Carlos Quentin in December. Quentin isn’t patient and has trouble staying healthy, but he does have power. If San Diego can get him 500 plate appearances and spell him with Chris Denorfia and Jesus Guzman, the Padres should get at least a couple more wins from left than they did last season.

Rockies, Second Base (2.3 WARP improvement)
The Rockies’ Jonathan Herrera and Chris Nelson experiments fell flat early last season, so they traded for A’s veteran Mark Ellis in June. Ellis was only a marginal improvement, and Colorado second basemen finished a collective half-win below replacement level.

The Rockies allowed Ellis to leave via free agency and traded low-upside arm Clayton Mortensen to the Red Sox for Marco Scutaro. From 2008-2011, only four shortstops contributed more to their teams than Scutaro’s 14.0 WARP. His bat won’t be quite as valuable an asset at second base, but his glove should be even better-equipped to handle the demands of his new position. It’s rare to see the Sox unload a quality player in search of salary relief, but in this instance, the Rockies benefited from Boston’s desire to stick to a budget.

​Thanks to Andrew Chong, Bradley Ankrom, and Rob McQuown for research assistance.

A version of this story originally appeared on ESPN Insider Insider.

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I'd add the Tigers' third base to this. Even allowing for Cabrera's defensive shortcomings, the difference between who they had there last year and Miggy is going to be substantial.
Yes, definitely, despite the dubious prospect of Cabrera playing a position other than first. The conceit of the article was that the improvement had to come from a new addition, though, so Cabrera and other position switchers didn't qualify (even though his move was a result of the Fielder signing).
Cabrera's not going to play 3rd for the Tigers. This experiment will be over about three weeks into spring training.
Ben, I am wondering what the cumulative small additions/subtractions you alluded to look like for the Jays' bullpen?

2012 back end manned by: Sergio Santos, Casey Janssen, FCordero, and Darren Oliver vs. the 2011 Kerosine crew of:

Jon Rauch, Frank Fran, Janssen, and Dotel.
" Angels first basemen produced 2.4 WARP, roughly an average total."
Wouldn't an average total be a WARP of 0.0?
No--WARP is wins above replacement level, not wins above average.
@Chiefsnark (first post)...that's assuming Cabrera actually lasts at 3B. Frankly, I don't see it lasting beyond the first month.
Giants catcher didn't factor into this? It should be a huge improvement if Buster Posey returns to his previous level of success.
Giants catcher was projected to improve by 2.0 WARP (and not because of a player acquisition, so it wouldn't have qualified for the article anyway).
Fair to expect the Brewers would have improved dramatically at 3B by replacing Casey McGehee with Casey McGehee and the Marlins would likewise at SS by replacing Hanley Ramirez with Hanley Ramirez.