MLB’s Pre-Debut Extensions Have Produced a Wide Range of Outcomes

The Mariners became the latest team to bet on their farm system Tuesday, signing top prospect Colt Emerson to an eight-year, $95 million contract. It’s the largest deal ever given to a player who has no major league service time.

Emerson was ranked fourth on our list of MLB’s top 50 prospects and projects to have All-Star upside. The 20-year-old shortstop is starting this season at Triple A after finishing there last year, and is on pace to earn a call up to Seattle in the next few months.

Given the scale of the Mariners’ investment in Emerson, continuing a trend that’s become ever the more prevalent in recent years, it’s worth evaluating the eight other players who landed contracts before ever appearing in a major league game—and whether those early investments have paid off.

Jon Singleton, Astros (2014)

Originally an eighth-round pick of the Phillies, Singleton was traded to the Astros in 2011 as part of a four-player package for Hunter Pence. Within a few years, the hulking first baseman was one of the Astros’ top prospects when the franchise opted to sign him to a five-year, $10 million extension in June 2014. The deal was worth up to $35 million. It didn’t turn out well.

In 114 games from 2014 through ‘15, he slashed .171/.290/.331, with 14 home runs, 50 RBIs, a wRC+ of 81 and -0.9 fWAR. That plus Singleton’s whopping 36.0% strikeout rate didn’t give Houston much reason to work out his issues during the Astros’ championship window that coincided with his struggles.

After playing in 19 games during the 2015 campaign, he didn’t see the majors again until returning to the bigs in 2023 with the Brewers. He was soon released after 11 uninspiring games with Milwaukee, and found his way back to the Astros. He enjoyed a fleeting revival with them in ’24, but shortly ran out of chances to revive his MLB career and is now a member of the Diablos Rojos del México in the Mexican League.

Scott Kingery, Phillies (2018)

You don’t remember Scott Kingery? Don’t worry, you’re not alone. The Phillies thought they had the next big thing when the then 23-year-old slashed .304/.359/.530 with 26 home runs, 65 RBIs and 29 stolen bases in 132 games at Double-A and Triple-A in 2017. After posting a 1.140 OPS in spring training, Philadelphia inked Kingery to a six-year, $24 million deal and put him on the Opening Day roster. Things didn’t end well for the 5’9” infielder.

As a rookie in 2018, Kingery hit .226 with a .267 on-base percentage while slugging .330. His 61 wRC+ was woeful, as was his -0.7 fWAR. He bounced back in ’19, slashing .258/.315/.474, with 19 home runs, 55 RBIs, a wRC+ 100, and a 2.1 fWAR. That wound up being the high point of his career. He struggled in the COVID-shortened 2020 campaign, posting a .511 OPS and -0.9 fWAR while producing a lowly 36 wRC+ in 36 games. He only played in 16 games for the Phillies over the next two seasons.

Kinger was traded to the Angels on Nov. 1, 2024, and played in 19 big league games in ’25. He hooked on with the Cubs this offseason and made the team’s Opening Day roster, but his expectations are far lower than they once were. The former top prospect has a career fWAR of -0.3.

Eloy Jimenez, Chicago White So — The Chicago White Sox signed Eloy Jimenez before he played a single MLB inning. | Kamil Krzaczynski-Imagn Images

Eloy Jiménez, White Sox (2019)

Jiménez was a top international free agent in 2013, and the Cubs gave him a $2.8 million signing bonus. By ’17, he was working his way through the system when the North Siders traded him to the White Sox along with Dylan Cease, Matt Rose and Bryant Flete in exchange for José Quintana. In March of 2019, the South Siders signed him to a six-year, $43 million contract and promoted him to the big leagues to open the season.

As a rookie that year, Jiménez slashed .267/.315/.513 with 31 home runs, 79 RBIs, a 115 wRC+ and 1.1 fWAR over 122 games, earning him a fourth-place finish in AL Rookie of the Year voting. He initially followed up well in his sophomore campaign, winning a Silver Slugger award by hitting .296 with a .891 OPS, 14 home runs, 41 RBIs, a 138 wRC+ and 1.5 fWAR. Unfortunately, injuries proved to be a problem after that.

Jiménez ruptured his pec during spring training in 2021, dealt with a hamstring injury in ’22 and had an appendectomy in ’23. The White Sox traded him to the Orioles in ’24. From ’21 through ‘24, he posted a .745 OPS with 50 home runs, 178 RBIs, a 107 wRC+ and 1.5 fWAR. On Nov. 2, 2024, the Orioles declined the option on Jiménez’s contract, instead opting to pay a $3 million buyout. He has been in the minors since, and is currently in the Blue Jays’ system.

Evan White, Mariners (2019)

Emerson isn’t the first player the Mariners have signed without any MLB experience, and Seattle’s front office either has marrow-deep certainty in him or collectively has a really short memory. The franchise selected first baseman Evan White with the 17th pick in the 2017 MLB draft, and two years later, in November ’19, signed him to a six-year, $24 million deal that could have paid him $55.5 million. It wasn’t a great idea.

White won a Gold Glove as a rookie in 2020, but in 54 games slashed a woeful .176/.252/.346 with eight home runs, 26 RBIs and a wRC+ of 67. He produced -0.1 fWAR. In ’21, he was even worse, slashing .144/.202/.237 with two home runs, a wRC+ of 24 and -0.7 fWAR in 30 games before having season-ending hip surgery. He hasn’t seen the big leagues since.

White dealt with sports hernia surgery in 2022, struggled with a groin strain in ’23, and was traded to the Angels in December of that year. He stayed with L.A. for two years despite not playing at all in ’25 and became a free agent after last season, and remains unsigned.

Luis Robert Jr., White Sox (2020)

In late 2016, Robert defected from Cuba at 19 years old with a world of promise in front of him. The White Sox signed him to a deal that included a $26 million signing bonus. He proceeded to crush minor league pitching and in 2019, hit .328 with a 1.000 OPS, 32 home runs, 98 RBIs and 36 stolen bases over three levels, finishing at Triple A.

Chicago had seen enough, and early in January 2020, they signed him to a six-year, $50 million deal with two option years tacked on. He made his MLB debut a few months later and quickly looked like a star.

Robert won a Gold Glove as a rookie during the pandemic-shortened season and finished as the runner-up for AL Rookie of the Year. Unfortunately, though, he suffered a torn hip flexor early in 2021 and played only 68 games that year, and was again limited to 98 games in ’22. He finally had a full season in ’23 and thrived, slashing .364/.315/.542 with 38 home runs, 80 RBIs, 20 stolen bases, a 129 wRC+ and 4.9 fWAR. Robert was named an All-Star and won a Silver Slugger. That was as high as he climbed.

The tools-heavy player who was once compared to Mike Trout posted a wRC+ of 84 in both 2024 and ‘25, and combined for 1.9 fWAR in those two seasons. He was traded to the Mets before the 2026 campaign, and is off to a hot start in New York, but there’s still a lot to prove before he fulfills his potential.

Milwaukee Brewers, Jackson Chouri — Milwaukee Brewers right fielder Jackson Chourio has become a cornerstone of the franchise. | Benny Sieu-Imagn Images

Jackson Chourio, Brewers (2023)

Chourio was one of the top prospects in baseball when the Brewers decided to sign him to an eight-year contract worth $82 million on Dec. 4, 2023. The right fielder made his big league debut on Opening Day in 2024 at 20 years old, but struggled to start his career.

Through his first 51 MLB games, Chourio hit .207 with a .575 OPS, but he turned it around over the rest of the season. In his final 97 games, Milwaukee’s young star slashed .305/.360/.527 with 16 home runs and 63 RBIs. For the season, he posted a wRC+ of 118 and an fWAR of 3.9. He took a slight step back in Year Two, slashing .270/.308/.463 with a wRC+ of 113 and 2.9 fWAR. But the potential is still there for the 22-year-old to become a massive star.

Colt Keith, Tigers (2024)

Keith broke out in 2023 when he hit .306 with 27 home runs and a .932 OPS over two minor league levels. He finished that breakout showcase at Triple A, and the Tigers loved what they’d seen from the former fifth-round pick so much they signed him to a six-year deal with $28.6 million in guarantees that could wind up being worth $82 million. They’ve gotten mixed results so far.

The 24-year-old infielder has had two solid MLB seasons, but hasn’t really fulfilled his potential. In 2024, he posted a .689 OPS and 13 home runs with a below-average wRC+ (95), and 1.7 fWAR in 148 games. In ’25, he played in 137 games, slashing .256/.333/.413 with 13 home runs, a 109 wRC+ and 1.6 fWAR.

Detroit’s outlay on Keith’s is far below market for a starting second baseman. If he never becomes a star, it’s probably still a fine deal. He’s only 24, so improvement could be on the horizon.

Cooper Pratt, Brewers (2026)

Pratt is a really interesting case, as he’s a guy who has struggled to hit in the minors, but he’s an elite defender. Despite that, the Brewers opted to give him an eight-year, $50.75 million contract on Monday.

In 2025, at Double A, Pratt hit .238 with a .691 OPS, but notably did log a .343 on-base percentage. He also hit eight home runs and 62 RBIs with a wRC+ of 107 in 120 games. His strikeout (15.2%) and walk (12.7%) rates were both good, and as stated, he’s an outstanding defender.

Pratt is likely to spend most or all of the 2026 season at Triple A. Despite his strong stature (6’3”), he doesn’t generate a lot of power. But if he makes the big leagues as a plus defender who can be an above-average hitter, the deal will likely pay off.