MLB Trades That Accidentally Built a Dynasty for the Other Team

by Jeremy Block - 6/29/2026

MLB trades that accidentally built dynasty for other team Mookie Betts

In any professional sport, some trades just don't age well. They look fine for a year, maybe two, and then one team's front office starts getting questions from the fan base while the other team throws a parade down Main Street after winning it all. Baseball has a long memory for this stuff, and these six trades prove that the best move a General Manager can make is sometimes the one he has no idea he's making.

These six trades are from six different decades of baseball where one team handed over the exact piece another franchise needed to go on a run, usually without realizing it until the standings made it obvious. Let's get into it.

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Babe Ruth to the Yankees (1920)

Selling off your franchise's best player while you're locked in a political war with the league's most powerful man sounds like a recipe for disaster, and that's roughly the spot Red Sox owner Harry Frazee found himself in when he sold Ruth to New York for cash and a mortgage on Fenway Park in 1920. The Yankees hadn't won a single pennant before Ruth showed up, and Ruth wasn't yet the player he'd become either, never hitting more than 29 home runs in six seasons in Boston.

That all changed fast. Ruth turned the Yankees into box office gold almost overnight, smashing his own home run record and pulling crowds big enough to justify building an entire stadium just to hold them. He'd clearly found his footing in pinstripes, racking up 54 homers in his very first season in New York, nearly doubling the mark he'd set the year before.

The Yankees would then go on to winning their first pennant in 1921 and their first title two years later, and from there the Bambino kept rewriting the record book almost annually, topping out at 60 home runs by 1927.

What people forget is that Ruth wasn't some finished product the Yankees got lucky with. He was already the best hitter in the sport when Boston let him go, but nobody, not even Ruth himself, fully grasped how much bigger he was about to get once he had an opportunity and a city's full support behind him. The Yankees bought the exact ingredients for a legend that hadn't fully cooked yet.

Lou Brock for Ernie Broglio (1964)

Coming off an 18-win season, right-hander Ernie Broglio was exactly what the Cubs thought they needed, so they shipped a young Lou Brock to St. Louis to get him. Brock was hitting just .251 at the time of the trade—the kind of hitting teams move on from when they feel they've seen enough. The Cubs thought they were buying proven production, but they were actually selling a decade and a half of top-tier base-running, elite base-stealing, and championship-level at-bats.

Brock caught fire the second he put on a Cardinals jersey, hitting .348 over the rest of that 1964 season. From there, St. Louis climbed all the way from eighth place to a World Series title over the Yankees that same October.

He would go on to swipe 938 career bases, make six All-Star teams, and help the Cardinals capture another ring in 1967. Broglio, meanwhile, went just 7-19 over the rest of his pitching career and was completely out of baseball by 1966.

Cubs fans have had plenty of company in their misery over the decades, but this trade stings a little extra because Chicago wasn't dumping salary or kicking off a rebuild. They genuinely, truly believed they were upgrading.

John Smoltz for Doyle Alexander (1987)

A 9-0 stretch run is the kind of thing that wins a division, and that's exactly what Detroit got out of acquiring Doyle Alexander in 1987, helping the Tigers edge past Toronto for the AL East crown. The cost? Nothing too crazy, at least at the time—a 20-year-old pitching prospect by the name of John Smoltz, who was sitting in Double-A with zero big-league experience. Detroit needed to win right then, and Alexander gave them exactly that. But the bill came due fast.

Smoltz hit the ground running almost immediately, posting a 2.94 ERA in his first full season with Atlanta. He didn't stop there. A few years later, he turned in a dominant 276-strikeout season, eventually anchoring the rotation for Atlanta's 1995 World Series championship team. By the end of his 20-year run with the franchise, Smoltz was a first-ballot Hall of Famer and the only pitcher in baseball history to record both 200 wins and 150 saves. Alexander, on the other hand, was out of the league within two seasons of the trade.

What makes this one brutal for Tigers fans specifically is the timing. Alexander's hot streak happened in real time during an actual, thrilling pennant race, while Smoltz's payoff took years to fully show up in the standings.

Jason Varitek and Derek Lowe for Heathcliff Slocumb (1997)

Decent closer numbers can mask a lot of problems until they suddenly can't. That is roughly what happened in Boston in 1997, before the Red Sox dumped their struggling reliever, Heathcliff Slocumb, for whatever they could get.

What came back from Seattle was a young catcher named Jason Varitek and a pitching prospect named Derek Lowe. Neither of them had done a single thing in the big leagues yet, but that changed like a flick to a switch.

Varitek went on to become the captain of the Red Sox, standing at the forefront of the franchise for 15 seasons while collecting 193 career home runs and driving in 757 RBIs. He became the only backstop in baseball history to catch four different official no-hitters, while serving as the main engine behind both the 2004 and 2007 championship runs.

Lowe’s path was just as legendary. He quickly became a dominant, league-leading closer with a 42-save season in 2000, then transitioned into a solid starter, where he posted a 21-win season in 2002 and won all three series-clinching games during that historic 2004 title run.

Slocumb, meanwhile, gave Seattle one mediocre season before giving the final wave out of the league entirely. Boston was just looking to clear bullpen space at the moment and walked away with two foundational pieces that helped snap an 86-year curse.

Lorenzo Cain and Alcides Escobar for Zack Greinke (2010)

A true ace was the missing piece in Milwaukee, and Zack Greinke fit the bill, having won an AL Cy Young in Kansas City two seasons prior. The Brewers sent back a package that included Lorenzo Cain, Alcides Escobar, and Jake Odorizzi, a group of names that meant nothing to anybody outside of Royals scouting reports at the time.

However, that all took a flip in no time. Cain developed into an All-Star center fielder and a Gold Glove winner, hitting .307 with 28 stolen bases during their championship season. Escobar became a fixture at shortstop, playing in all 162 games three different times and racking up over 1,100 hits in a Royals uniform. Both players were huge assets, fueling back-to-back World Series appearances in 2014 and 2015, and finally lifting the crown on that second try.

On the other side, Greinke won 25 games over a year and a half in Milwaukee, but with the team slipping out of the race in 2012, the Brewers flipped him to the Angels at the deadline. He never delivered the deep October run Milwaukee actually sacrificed their future to get.

Kansas City had been irrelevant for nearly two decades before this trade unexpectedly handed them the blueprints to end that drought. Almost nobody outside of the Midwest paid attention to this deal when it happened, which tells you everything about how different these things look in real time versus years down the road.

Mookie Betts to the Dodgers (2020)

Refusing to pay market rate for an MVP-caliber outfielder is a choice, and it's the one Boston made heading into a shortened pandemic season, sending Mookie Betts to Los Angeles rather than committing long-term. The Dodgers wasted zero time locking him up with a 12-year, $365 million extension, treating the move as the final piece of a roster that had been knocking on the door for years without breaking through. It’s safe to say they found exactly what they needed.

Betts delivered on everything Los Angeles hoped for and then some, sliding into shortstop duties on top of his usual outfield work while racking up Gold Gloves and Silver Sluggers along the way. He was a key piece of three World Series titles in Los Angeles, including back-to-back championships in 2024 and 2025, helping turn the Dodgers into the sport's modern dynasty. What Boston got back has had its moments but hasn't come close to replacing what walked out the door.

More than any other deal on this list, this trade is different because everybody understood exactly what was happening the day it was announced. There was no scouting miss, no surprise development years down the line. Boston knew Betts was great and traded him anyway.

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Start:	June 29, 2026 @ 7:10 PM
Expert:	Tony George
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MLB Trades That Accidentally Built a Dynasty for the Other Team

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