Some Hot Stove moves are all about turning a strength into a greater strength (as evidenced by the Yankees' acquisition of Aroldis Chapman) or filling a hole newly created by free agency or trade (such as the Cubs signing Jason Heyward to replace Dexter Fowler).
But usually, it's all about addressing weaknesses.
With that in mind, here were the worst-performing teams at each position, per Baseball Reference's WAR calculations, and what (if anything) those teams have done to upgrade those spots.
Starting pitching: Tigers (WAR: minus-8.1)
A major statistical regression for Victor Martinez and Miguel Cabrera's first-ever extended injury absence were key contributors in the Tigers' fall from grace last season, but far from the only contributors. A once-great rotation went backward in a big way, despite David Price's presence for the first four months. Justin Verlander also had his first DL trip, Afredo Simon and Anibal Sanchez were surprisingly far below league average, Shane Greene imploded, etc.
We entered the winter certain the Tigers would target at least one and likely two starting additions (on top of the additions of Daniel Norris and Matt Boyd in the Price trade). Less certain was whether they'd dabble in the upper crust of the free-agent market. But Mike Ilitch opened the wallet yet again, with the Tigers becoming the first team to give a Tommy John alumnus, Jordan Zimmermann, a guarantee of more than $100 million. He should slot in nicely alongside Verlander, who made serious strides in the second half in reclaiming his old fastball, near the top of the rotation. Less-exciting was the two-year, $16 million deal with Mike Pelfrey, who had a solid '15 despite some shaky peripherals in Minnesota.
By and large, you have to feel better about the Tigers' depth of options than you did a year ago.
Relief pitching: A's (minus-6.0)
What a hot mess that Oakland bullpen was last season. As we've discussed in this space before, it was the single biggest reason the A's, who finished 68-94, finished significantly below both their Pythagorean (77-85) and third-order (80-82) win expectancies.
The prolonged absence of Sean Doolittle (0.734 WHIP, 11.13 strikeout-to-walk ratio in '14) really hurt, as did having four guys with 38 relief appearances or more (Fernando Abad, Evan Scribner, Dan Otero and Ed Mujica) notching ERAs north of 4.00 (in a big home ballpark, no less).
All four of those guys are gone now (as are Drew Pomeranz, Arnold Leon and Pat Venditte), and Doolittle is healthy. Beyond that, the A's have added Ryan Madson (three years, $22 million), John Axford (two years, $10 million) and trade acquisitions Liam Hendriks, Marc Rzepczynski and J.B. Wendelken. Newly added veteran Rich Hill will get his shot in the rotation but could also possibly go back to relief work as the year evolves.
Who knows if this 'pen is better, but at least it's drastically different.
Catcher: Mariners (minus-3.9)
Pretty rare when you can call a guy who hit .188 last year an upgrade, but so it is with the M's. Mike Zunino is one of multiple stalled former top prospects who cost Jack Zduriencik his job. It's pretty clear the kid was rushed to the bigs before he was adequately prepared, and his 2015 season, in which he had a .174/.230/.300 slash in 112 games, was rock bottom.
New general manager Jerry Dipoto wasted no time addressing this backstop burden, signing Chris Iannetta, an old friend from his Halos days, to a one-year, $4.25 million contract and also adding Steve Clevenger in the Mark Trumbo trade with the Brewers. Zunino, as a result, is likely ticketed for Triple-A, where he spent some time last year.
Of course, Iannetta didn't exactly rip it up last year, and he's entering his age-33 season. But his abnormally low batting average on balls in play (.225) and the seven seasons in which he's produced at a league-average rate combine with his impressive pitch-framing abilities to make this a potentially savvy pickup.
First base: Phillies (minus-3.6)
Contrary to what was speculated here and elsewhere in the lead-up to 2015, Ryan Howard did not establish himself as a viable trade chip last season, even with the Phils willing to eat the vast majority of his remaining contract. So they're still stuck with Howard and the $35 million remaining on his deal ($25 million for this year and a $10 million buyout for '17).
With the Phillies still very much in punt mode, it obviously doesn't make any sense for them to take a serious aim at upgrading this position. And while Darin Ruf performed fairly well in Howard's absence in the final month of '15, he's 29 and really just a platoon option against lefties. It is what it is, as people say (when they don't know what else to say).
Second base: D-backs (minus-2.3)
Though they have the makings of an elite NL offense for '16, the D-backs' obvious trouble spot, for now, remains second base, where a 23-year-old Chris Owings (.587 OPS) and a 33-year-old Aaron Hill (.640) were at disparate ages but found common ground in their inability to produce.
Because Arizona invested so much in terms of financial capital and prospect capital in addressing their rotation, they don't have much to work with to fix other areas of concern (the bullpen being another). They had dialogue with the Reds about Brandon Phillips, but that went nowhere, and they've kicked the tires on Howie Kendrick, but that, too, has been a dead-end, to date.
So it's status quo, for now, at second base. But at least age is on Owings' side, even if his .639 OPS in nearly 1,000 big league plate appearances doesn't portend big things to come.
Shortstop: Orioles (minus-2.6)
Not much to see here. J.J. Hardy had a truly miserable season in the first year of the three-year, $40 million contract extension he signed at the end of '14. He played the entire season with a torn labrum in his non-throwing shoulder, and that contributed to his woeful .219/.253/.311 slash. A slugging percentage that fell 61 points from '13 to '14 fell another 61 points from '14 to '15. Not good.
Rather than having surgery on the shoulder, Hardy has spent his winter strengthening it. Especially with so many other holes to fill, the O's have obviously not made any attempt to supplant Hardy at short. They simply need him healthier and more productive.
Third base: Red Sox (minus-2.7)
Yep, another newly signed AL East dud on the left side of the infield. Pablo Sandoval was a big bust in the first year of his five-year, $95 million contract -- a bust that, if our eyes don't deceive us, kept quite literally getting bigger and bigger as the year evolved. When your season is memorable mostly for that time you liked a photo on Instagram during a mid-game bathroom break, suffice it to say your stats wound up in the toilet. Just as concerning as the steep regression in production was the alarming erosion in defensive play, too. Per FanGraphs' WAR calculation, Sandoval was the worst-performing regular in the Majors last season at this or any position.
Stop me if you've heard this before, but the Panda's on a new diet and workout program again this offseason. He's turned his career around before when the questions about his weight and dedication came pouring in, and it's time to do so again.
Left field: Nationals (minus-3.4)
Jayson Werth's left wrist injury made for a drastic decline in playing time and performance, and the Nats struggled to piece it together in left, with young Michael A. Taylor (who also spelled an injured Denard Span quite a bit in center) and converted outfielder Clint Robinson getting the most playing time in Werth's stead.
It obviously didn't add up to much, and you have to wonder how much the 36-year-old Werth, who himself recently admitted "you can't outrun Father Time," has left in the tank, particularly after three surgeries and four surgeries to that wrist.
The good news? The trade for Ben Revere added a versatile, speedy defender to the mix, and he can spell Werth on occasion or relegate the athletic Taylor to fourth outfielder status. However the playing time shakes out, the Nats' outfield depth is definitely better than it was.
Center field: Giants (minus-3.3)
The loyalty the Giants showed to Angel Pagan in the form of a four-year, $40 million contract after he helped lead them to the 2012 title has not been rewarded. Pagan played just 167 games in 2013-14, and his 77 OPS+ made him a bottom-of-the-barrel center fielder in '15, which he played at the age of 33. He's entering his walk year, and he had a solid September after spending much of August on the DL. So maybe he's due for a bounceback '16, or maybe he'll cede more at-bats to Gregor Blanco.
Whatever the case, that's now likely an issue in left field, not center, because the Giants went out and signed Span to join Jeff Samardzija and Johnny Cueto and complete the bounceback free-agent trifecta. Span is 32, and he had core muscle and hip surgeries last year. So he's no safe bet, by any means. But if he's healthy, he's a high-contact, fleet-footed leadoff presence who fits in perfectly with the Giants' offensive profile.
Hard to say what kind of range Span will have in center following those injuries, but -- on paper, at least -- this looks to be an offensive upgrade.
Right field: Twins (minus-2.6)
Obviously, the WAR stat wasn't nearly as impressed with what Torii Hunter brought to the Twins at age 39 as the Twins themselves, who understandably raved about his impact on a young clubhouse, were. Hunter's defense, of course, was a mere shadow of what it once was, and the 22 homers and 22 doubles were offset by career lows in batting average and on-base percentage. Relative to your average 39-year-old, it was an impressive season. Relative to the rest of the current crop of right fielders, not so much.
The Twins' outfield situation, in general, is pretty fluid, but their plan for now is to go the experimental route in right, with Miguel Sano coming into camp with an opportunity to prove himself capable of handling the position. Sano's original position at the hot corner is still in the hands of Trevor Plouffe, Joe Mauer's at first and Korean import Byung Ho Park will handle the DH duties. So the 268-pound Sano, who had a monster rookie year (18 homers, .916 OPS in 80 games), will take his big-but-athletic body out to a position he's never previously played. It's bound to be one of the more intriguing storylines of the spring.
Eddie Rosario is another corner-outfield option coming off a strong rookie year, but he's currently expected to play left. If the Sano experiment fails, the Twins could eventually turn to German-born prospect Max Kepler, who won the organization's Minor League Player of the Year honors after smacking 54 extra-base hits and swiping 19 steals at Double-A New Britain.
Designated hitter: A's (minus-2.7)
This is not a list you want to appear on twice. Worse yet, the A's got here on the back of their highest-paid player, Billy Butler.
It was a surprise when the A's gave him a three-year, $30 million deal after a down year in his final season with the Royals, and his 2016 stat line - in terms of OPS+ (96), on-base percentage (.323), total bases (210) - were remarkably similar to '15. Ol' Country Breakfast was a bust -- a DH without enough "H." Butler doesn't have the speed to survive his recent groundball/flyball rates. He needs to drive the ball more consistently.
The A's obviously made every effort to address the 'pen, but they're simply stuck with Butler for the time being.
* * *
Anthony Castrovince is a Sports on Earth contributor and an MLB.com columnist. Follow him on Twitter @Castrovince.