An active offseason doesn’t guarantee a jump in wins. At this stage of the year, though, it is worth looking at which teams have done the most to address their weaknesses.
Being a great team is not only about star talent. Well-rounded rosters are often more effective over the course of a full season. An explosive lineup can only carry a team so far, just as a dominant rotation cannot win games without run support.
With that in mind, here are the five most improved teams heading into the 2026 MLB season.
Boston Red Sox
Willson Contreras, owner of a 126 OPS+ and 27.3 homers per 162 games over the last four seasons, is a clear upgrade at first base. Boston ranked 27th in fWAR at the position in 2025.
The Red Sox were middle of the pack in xERA last season. Despite some solid results, the pitching staff needed reinforcements behind Garrett Crochet. Sonny Gray and Ranger Suárez address that need, with Brayan Bello and José Oviedo projected to round out the rotation.
Boston did lose Alex Bregman and did not add another marquee bat in free agency, but Contreras’ production is flying under the radar. The trade for Caleb Durbin was also a shrewd upside move that fills a clear roster need.
It was not the offseason many in Boston hoped for. Kyle Tucker, Bregman, and Bo Bichette signed elsewhere, but there is little question the Red Sox improved after overachieving in 2025.
Pittsburgh Pirates
Seventh in ERA and 29th in wRC+, it was clear what the Pirates needed to address this winter. The additions of Brandon Lowe, Ryan O’Hearn, and Marcell Ozuna should give this offense a much-needed overhaul.
Pittsburgh is not suddenly going to become a top-10 offense, but this group is a better fit for a team built around one of the stronger rotations in baseball, featuring Paul Skenes, Mitch Keller, and Braxton Ashcraft.
It is reasonable to expect Lowe, O’Hearn, and Ozuna to combine for at least a 115 wRC+ and around 50 home runs. Spencer Horwitz was the only Pirate close to that level of production last season.
Gregory Soto and Mason Montgomery should also help stabilize the bullpen. With even a league-average offense, the Pirates have the profile of a wild card contender, a significant step up from their 71-win 2025 season.
New York Mets
The Mets did not land Kyle Tucker or Dylan Cease, and for a while the offseason felt underwhelming. New York ultimately delivered in a big way, though, with a string of marquee acquisitions.
The loss of Edwin Díaz was addressed by signing Devin Williams, Luis García, and Luke Weaver. Tobias Myers also arrived in the blockbuster deal that sent Freddy Peralta from Milwaukee to New York.
In the lineup, the departure of Pete Alonso was not popular, but the Mets responded by signing Jorge Polanco and Bo Bichette and trading for Marcus Semien and Luis Robert Jr.
A second-half collapse kept the Mets out of the playoffs in 2025, but every area of the roster has improved this winter. While Peralta is the only major rotation addition, the expected development of prospects Nolan McLean and Jonah Tong points to a staff that should take a step forward.
Chicago Cubs
Just as the Red Sox lost Bregman, the Cubs parted ways with Tucker. Chicago moved quickly to replace him, signing Bregman to take over at third base. Edward Cabrera, who posted a career-best 105 ERA+ in 2025, arrived from Miami in a trade.
The Cubs also invested in the bullpen, signing veteran relievers Hunter Harvey, Phil Maton, Jacob Webb, and Hoby Milner. Caleb Thielbar was re-signed as well.
Starting pitcher Jaxon Wiggins, a second-round pick in 2023, is expected to reach the majors at some point in 2026. The return of Justin Steele should also give the rotation a significant boost compared to last season.
It is not guaranteed the Cubs win more than the 92 games they recorded last year, but their floor is clearly higher than it was entering 2025.
Detroit Tigers
With Reese Olson and Jackson Jobe sidelined, the Tigers needed to reinforce their rotation. Thankfully, for everyone interested in the long-term health of baseball, Detroit did not trade away the sport’s premier pitcher.
Instead, they paid up for Framber Valdez and Justin Verlander to slot in behind Tarik Skubal. Valdez gives Detroit arguably the best one-two punch in the majors, and Verlander appeared to rediscover his form in the second half last season, making him a valuable third or fourth starter.
After ranking 20th in bullpen xERA and 27th in reliever K-BB% in 2025, the Tigers also addressed the back end by signing Kenley Jansen and Drew Armstrong.
There is little doubt Detroit is the clear favorite in the AL Central. They may also have the most complete roster in the American League.
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