What would it cost for Marlins to extend sensational rookie Jakob Marsee?

This Miami Marlins team is not quite good enough to be playing meaningful games throughout September, but a lot of the individual pieces look like long-term contributors, and that makes this 2025 season an important step in the right direction. It was a quiet trade deadline for the Fish and it could be a quiet winter as well because of how much young talent is already in place. The key question is which players are worth truly building around and inking to contract extensions that go beyond the standard six years of club control.

The franchise's top priority should be extending Eury Pérez. In a full year's worth of starts at the major league level, he has posted an earned run average that's 39% better than the league average while being the youngest of all MLB starters during that span. Gifted with a unique physical build and arguably the nastiest pitch in baseball (his four-seam fastball), Pérez has the upside to be generational. But he is on track to reach free agency at age 26, which means the Marlins could miss out on several of the most valuable seasons of his career if they don't act quickly. The complication is, Pérez would be so highly coveted on the open market, there may not be a number that Miami's front office can responsibly offer him to justify delaying his FA eligibility.

Meanwhile, All-Star Kyle Stowers has unquestionably made the biggest impact on the Marlins in 2025. A minor oblique injury will dilute his final overall numbers, but he has emerged as a trustworthy, middle-of-the-order bat. Stowers is under control through age 31 and no longer plays a premium defensive position on a regular basis. His MLB track record is also uneven, including sub-replacement-level performance last season. As much as fans want the Fish to express their gratitude to him in the form of a multi-year deal, the urgency to do so isn't really there.

In a microscopic sample of 89 plate appearances, Jakob Marsee is looking like the ideal extension candidate. Marsee's well-rounded skill set has propelled him to a historically good first month in the majors. Also, he's represented by an agency, Dynamic Sports Group, with a relatively low profile in the baseball world and presumably eager to change that. More so than any other Marlins player, a contract covering his pre-arb, arbitration and early free agent years could be mutually beneficial.

An important caveat: I don't think Marsee will stay on this otherworldly pace through season's end. If he does—if he continues to perform like literally the best player in Major League Baseball—I have a difficult time imagining him seeking an extension. Somebody who has yet to experience one iota of adversity through two full months at the highest level of competition ought to continue betting on themselves.

My homemade rest-of-season projection for Marsee clones most of his current rate stats and counting stats while assuming a drop-off in his luck on balls in play. Let's go with three fewer singles remaining than he's recorded so far, two fewer doubles and one fewer triple. Even that is very generous to Marsee.

This would result in the following rookie stat line: .308/.382/.641, 8 HR, 14 SB, 11.2 BB% and 23.6 K% in 46 games. That should generate approximately 3.0 fWAR.

One other thing. As I got several hours deep into this exercise, I concluded there is enough analytical and entertainment value in here to justify charging money for it. If you are already a Fish On First SuperSub, you may continue scrolling without interruption! The rest of you will soon be implored to sign up. SuperSub support is absolutely vital to our survival.

Relevant Contract #1: Brandon Lowe

Prior to the 2019 season, Brandon Lowe and the Tampa Bay Rays agreed on a six-year, $24 million extension with club options for 2025 and 2026. If extended now, Marsee should insist on significantly more guaranteed money than Lowe got.

You may be surprised by how much they have in common.