These Are Dates Each Of Red Sox's 'Big 3' Prospects Will Make MLB Debuts

Some tough calls coming for the Sox decision makers...

Kristian Campbell comes off the field during a Red Sox Spring Training game on March 11, 2025, at JetBlue Park in Fort Myers, Florida. / WooSox Photo/Ashley Green / USA TODAY NETWORK via Imagn Images

It's rare to find a group of prospects who can steal the thunder from a team hoping to make the playoffs in Major League Baseball, but the Boston Red Sox's "big three" are doing exactly that.

Outfielder Roman Anthony, utility player Kristian Campbell, and shortstop Marcelo Mayer have electrified fans across the sport this spring as they draw closer to their Red Sox big-league debuts. Each will impact the 2025 season at some point--it's just a question of when.

So why not throw out some predictions? These are the exact dates Red Sox On SI predicts each of the "big three" will make their MLB debuts.

Kristian Campbell: Mar. 27 (at Texas Rangers)

If the Red Sox had to make a decision at this exact moment, it's dicey whether Campbell would make the roster. He's still just 5-for-30 in big-league spring training action, though his opposite-field home run in the Spring Breakout exhibition certainly helps his case.

But there's a bigger picture to consider here. The Red Sox are not-so-secretly planning to move Rafael Devers off third base, and it's a lot easier to sell that move to him if the team has a stud keeping Alex Bregman from playing second base.

David Hamilton has been great this spring, so no offense intended, but it's a lot more insulting to Devers if he's moved to designated hitter to clear room for a 27-year-old with 113 big-league games under his belt.

Campbell will have to step up in the final hours to win the job, but that's what we're predicting he'll do.

Roman Anthony: Apr. 18 (vs. Chicago White Sox)

It was extremely tempting to put Anthony on the Opening Day squad alongside Campbell. But Wilyer Abreu is suddenly looking as if he'll be healthy for the Texas series, and Boston needs to ensure Anthony is getting everyday reps from day one of the regular season.

But the minute the Red Sox send Anthony to Triple-A, he'll make it painfully obvious he doesn't belong there. He put up a .463 on-base percentage there as a 20-year-old last summer, and all he's done since is train and obsess about making it to the show.

The Red Sox will find an excuse to get Anthony in the lineup in April no matter how solid their outfield picture looks right now. An injury will make things all too easy, but if Abreu or Ceddanne Rafaela struggles offensively, Anthony is going to quickly get his turn.

Marcelo Mayer: Aug. 15 (vs. Miami Marlins)

Mayer has performed the best of the three this spring and in a dream world, we wouldn't have to wait this long to see him impact the big leagues. But save for another Trevor Story injury (knock on every piece of wood you can find), what is his path to playing time?

Shortstop? That's Story's spot as long as he's making over $20 million per year. Third base? Alex Bregman is making $40 million. And the Red Sox would prefer to have Campbell solidify the starting second base job, which will leave room for Anthony to play every day in the outfield.

The Red Sox can afford to take their time with Mayer because he's got to prove, at this point, that he can make it through a full, healthy big-league season. Eventually, he'll force their hand with his bat.

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