There are multiple ways to build a successful baseball team, but if recent history has taught us anything, depth is an important (and often overlooked) factor. Last season, the Red Sox won the World Series off the back of a deep roster that had few weaknesses. Boston’s success stood in stark contrast to the shortcomings of the Blue Jays and Yankees, who each succumbed to poor performances and injuries at multiple positions.

In many ways, then, simply avoiding a roster spot that is a veritable black hole in production is as important (and cheaper!) as signing a superstar to a big contract. With this in mind, I examined five teams that made important upgrades to positions that, last year, had provided them with nothing but subpar production:

(Note: All statistics, including WAR figures, taken from FanGraphs.com)

The Marlins had a bevy of subpar positional performances in 2013, and the team’s output at catcher was no exception. Marlins catchers produced -1.8 WAR last season, the lowest mark in the majors, as a platoon of Jeff Mathis and Rob Brantly proved woeful offensively. Miami backstops batted a collective .192/.249/.280 and finished with a .235 wOBA, the worst offensive performance by any group of catchers in baseball.

It might be more surprising, however, that the team addressed this issue in free agency, signing Jarrod Saltalamacchia to a team-friendly, three-year deal in December. The switch-hitting Saltalamacchia doesn’t come without shortcomings (most notably, a career 29.4% strikeout rate), but he will be a massive upgrade at catcher for the Marlins. The seven-year veteran is still relatively young for a free agent at 28, and has some pop in his bat, posting ISOs of .215, .232, and .192 over the past three seasons. His .372 BABIP (by far a career high) indicates that his .273 batting average will likely drop back towards the .230-240 territory, but a catcher who can still get on base over 30% of the time and provide some pop with his bat will be a big upgrade for Miami.

Milwaukee Brewers, First Base:

No team suffered from a worse positional performance in 2013 than the Brewers did at first base. A platoon of Juan Francisco and sabermetric punching bag Yuniesky Betancourt combined for an astounding -4.8 WAR, striking out 230 times and walking on just 47 occasions in 932 plate appearances. Measuring just by WAR, Milwaukee’s first base production last season ranks as the worst of all time in terms of single season performances at first base.

That type of historically bad production just has to improve, and even if Mark Reynolds isn’t a particularly exciting option, platooning Reynolds with Francisco will be a serviceable alternative in comparison. The 30-year-old Reynolds is a career .238/.359/.475 hitter against southpaws (he had a 103 wRC+ against lefties in 2013), while Francisco finished with a 104 wRC+ and .443 slugging versus righties last year. None of this is overly exciting (nor does the pair serve as a long-term solution), but if the two can just perform at replacement level, they will have gained the Brewers nearly four wins in 2014.

I too was surprised to see the Cardinals rank so low at third base, as their -0.9-WAR production at the hot corner was the worst in baseball last year. A banged up David Freese hit just .262/.340/.381 and played poor defense (-16.5 UZR and -14 defensive runs saved), while back-up Daniel Descalso didn’t fare much better (80 wRC+).

That should change in 2014 with Freese now in Los Angeles and Matt Carpenter sliding over to third base. Carpenter’s high-contact skill set isn’t your typical third base profile, but the 28-year-old finished with 7.0 WAR in 2013 and the sixth-highest line-drive rate in the majors at 27.3%. Moving Carpenter to third and going with some type of time-share between Mark Ellis and Kolten Wong at second should help St. Louis improve their infield production mightily, especially at third base.

Houston Astros, Center Field

The Astros received poor performances almost across the board last season, including at all three outfield positions. Brandon Barnes actually gave Houston adequate value in center, but now that he and Jordan Lyles have been shipped away to Colorado for Dexter Fowler, the team’s long-term outlook in the outfield is vastly improved. Questions surround Fowler’s offensive ability away from Coors Field (he compiled a 96 wRC+ on the road in 2013), but his speed and defensive skills make him a valuable player regardless.

Plus, the Astros can also expect highly regarded prospect George Springer to arrive on the scene sometime in 2014. Some worry over Springer’s propensity for strikeouts, but his plus power and speed combine to give him intriguing (and potentially difference-making) upside. With Springer and Fowler pegged as future above-average contributors, Houston’s outfield should already be improved this season. Even if they remain at the bottom of the AL West, the Astros are clearly making progress in re-tooling a barren major league roster.

Philadelphia Phillies, Right Field:

Like the Astros, the Phillies outfield was quite poor in 2013, combining for -2.7 WAR across all three outfield positions. Out in right, a combination of Delmon Young, John Mayberry, and Darin Ruf batted a collective .226/.292/.379, while fooling no one in regards to their Gold Glove credentials.

Marlon Byrd isn’t a particularly exciting solution, but he will be an upgrade over Philadelphia’s right field options last season. No one should expect Byrd to be worth 4.1 WAR again in 2014, but the 36-year-old did make legitimate changes to his approach last year. As Jason Collette noted over at FanGraphs in November, Byrd sold out for power, posting a 37.0% fly-ball rate (his highest since 2009) and the lowest ground-ball rate of his career in 2013. Assuming he doesn’t fall prey to too many strike outs, Byrd’s power should play again this season in the homer-friendly confines of Citizens Bank Park. At least in 2014, this means the Phillies have likely found themselves a cheap upgrade in right field.

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Alex Skillin is a writer and editor at Beyond the Box Score and also contributes to SB Nation's MLB newsdesk. He writes, mostly about baseball and basketball, at a few other places across the Internet. You can follow him on Twitter at @AlexSkillin.