Five biggest MLB offseason moves that will shape the 2026 season

Opening Day is almost here, but the excitement around the 2026 MLB season has been building for months. The 2025-26 MLB offseason certainly saw its share of drama with big names on the move for new adventures.

As the Official Ticketing Partner of Major League Baseball, SeatGeek keeps a close eye on all the action around the league, because every headline-making move over the offseason could shape tomorrow’s must-see matchup at the ballpark.

Biggest 2025-26 MLB offseason moves

From the reigning World Series champs adding an MVP-caliber player to a franchise icon making a stunning departure in free agency, here are the five biggest moves from this past offseason that will have the biggest impacts during the 2026 MLB season.

Kyle Tucker joins the reigning champs in L.A.

Tucker has quietly been one of baseball’s more well-rounded players. The star outfielder hits for average and power, draws walks and plays great defense in the outfield. He regularly was overshadowed during his time with the Astros in Houston, but he put together a very nice season in Chicago for the Cubs in 2025 with another .800+ OPS season. Now, he joins a team that somehow got even better in the Dodgers. 

The reigning champs have stars across the board from Shohei Ohtani to Blake Snell to Mookie Betts. Tucker may very well be the second-best player on the team now as he’s in his prime and has made four straight All-Star Games with 22+ home runs each of the last five years and 25+ steals in three of the last years. 

Tucker makes an already dangerous Los Angeles lineup even more dangerous with his mix of contact skills, power, elite eye and speed.  

Cubs tab Alex Bregman to replace Tucker

The Cubs lost Tucker to the Dodgers, but they aim to replace his production with another former Astros star in Bregman. The veteran third baseman signed with the Red Sox last year and had an .821 OPS in 115 games, parlaying that into a lucrative contract with the Cubs. 

Chicago made the postseason last year and has an exciting young core, but Bregman is a proven winner who should really raise the floor of the team’s lineup with his blend of power, contact and ability to work walks while not striking out. Plus, few players have more postseason experience than Bregman, who has two World Series rings and played in the playoffs each of the last nine years, only missing out on the postseason in his rookie campaign in 2016. 

Pete Alonso leaves Mets for Orioles

No player has hit more home runs in a Mets uniform than Alonso, who swatted 264 across seven seasons in New York. He tested free agency last offseason and wound up betting on himself and returning to the Mets on a short-term deal. That decision proved wise as the veteran first baseman slashed .272/.347/.524 with 38 home runs and 126 RBI in his final season in New York. 

He parlayed that into a lucrative five-year deal with the Orioles, who needed more offensive production after a surprisingly poor 2025 showing. Alonso instantly gives Baltimore a dynamic 1-2 punch alongside superstar shortstop Gunnar Henderson, and if other young players like Adley Rutschman perform better this season, the Orioles could have one of baseball’s most dangerous lineups. 

Framber Valdez reunites with former manager in Detroit

Valdez had been a mainstay in Houston’s rotation for years, but he’s now in the Motor City, reuniting with former Astros skipper AJ Hinch. Valdez is one of the game’s best at keeping the ball in the yard and eliciting ground balls with an elite sinker-curveball combination, and 2026 was more of the same from the southpaw as he had a 3.66 ERA in nearly 200 innings of work. 

The Tigers’ lineup is a bit of a question mark as they aim to return to the postseason and build on an ALDS run, but there’s no denying how elite that rotation can be. The Tigers have the game’s best pitcher in two-time Cy Young winner Tarik Skubal, and Valdez is now slotted in as arguably the best No. 2 starter in the game.

Seattle trades for Brendan Donovan, re-signs Josh Naylor

We’ll cheat a bit here with a 2-for-1, but both players provide a similar need for the Mariners. Seattle’s been a good to great team since 2021, but the lineup has had an issue with strikeouts. That issue played a big role in the team losing to the Blue Jays in the ALCS in October. 

Naylor was part of that group and provided length and pop to the lineup while not striking out much at all. He signed a big contract to return to Seattle in one of the first big moves any team made this offseason. Then, the Mariners were able to make their second big swing of the offseason by trading for Donovan. 

The former Cardinals star hit .287 while making his first All-Star team. Donovan will slide in at either second or third base, but his contact-focused bat will be huge for the top of Seattle’s lineup ahead of sluggers like Cal Raleigh and Julio Rodriguez.