What can the Red Sox get if they trade Mookie Betts?

Mookie Betts turned 27 on Monday, an age that often falls squarely within the realm of a player’s peak. And in the case of Betts, that peak has few peers not just among the landscape of active big leaguers but in baseball history.

For all of the talk of Betts suffering through a down year in the first half of 2019, his year-end numbers — a .295/.391/.524 line with 29 homers and 74 extra-base hits along with 16 steals and elite defense in right — once again underscored that his baseline performance is that of one of the best hitters in the game. He is not merely good or very good but instead, after four straight All-Star seasons and likely four straight top-10 finishes in AL MVP voting, off to a career start that places him among inner-circle Hall of Famers.

Since his first full big league season in 2015, Betts has been worth 39.7 Wins Above Replacement in the calculations of Baseball-Reference.com, 10th best from ages 22 through 26 of any position player in baseball history, just ahead of players such as Hank Aaron, Willie Mays, and Joe DiMaggio.

Of course, Betts benefits because his elite defense factors into the WAR calculation, while earlier generations did not get graded with Defensive Runs Saved or Ultimate Zone Rating or other advanced metrics.

Even so, looking only at the offensive impact (as measured by offensive WAR) by Betts, the five-year run he just concluded still places him squarely in Cooperstown-caliber company.

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This just in: Betts is a franchise talent, thus making rather unenviable an incoming Red Sox GM’s task of deciding whether to trade the superstar.

But that executive won’t be the first to face such an uncomfortable crossroads.

There have been times when teams either traded or explored trading elite talents as those players, like Betts, moved within one year of free agency.

A look at some of those deals (and nondeals) offers some clues as to the potential landscape facing the Red Sox with Betts.

Ken Griffey Jr.

When the Mariners hired Pat Gillick after the 1999 season, the Hall of Fame executive faced a situation analogous to that confronting the Red Sox. An expected 1999 contender instead floundered in a third-place finish in the AL West, at a time when two superstars — Ken Griffey Jr. and Alex Rodriguez — were within a year of free agency.

Gillick thought there was no chance of re-signing Rodriguez before he hit free agency. Griffey, meanwhile, had turned down what would have been an eight-year, $148 million offer from Seattle — but not because of a desire to maximize earnings in free agency following the 2000 season. Instead, as he readied for his age-30 season, Griffey wanted a chance to play closer to his Orlando-area home, particularly in spring training. He made a strong plea to be traded. Gillick resigned himself to doing so, while keeping Rodriguez in his final pre-free-agent season.

“[But] you’ve got an obligation to fans, an obligation to ownership, an obligation to the players on your team that you can’t pull away two talents,” said Gillick. “I think it would have been a bit much for people to stomach if we’d have dealt Rodriguez also.”

The Mariners were constrained in trying to deal Griffey, who had the right to veto any deal. He identified a select few clubs to which he’d accept a trade, and, over months, Gillick worked out a deal for a four-player package anchored by outfielder Mike Cameron and righthander Brett Tomko.

“I would say at the time we got probably 60 or 70 percent of what we thought we should have gotten for him, and probably we only got that much because we were dealing with Cincinnati and the press knew it, so there was a bit of leverage with Cincinnati,” recalled Gillick.

Cameron had been a late addition to the package sought by the Mariners, a replacement for Pokey Reese. Cameron ended up being a solid five-tool contributor for Seattle en route to an ALCS berth. The following year, the Mariners used savings from the departures of Griffey and, after 2000, Rodriguez to add Ichiro Suzuki as well as Bret Boone, both of whom emerged as MVP candidates for Seattle en route to a 116-win season and another ALCS berth in 2001. Seattle captured enough value to survive a grim two-year task.

“You can’t waste the money,” said Gillick. “I guess it worked out, with what the outcome was in 2000 and 2001. If we’d have fallen on our faces those two years, it probably would have been looked at from another angle. But since we did well, the public and the fans and the sports people were satisfied that we probably did the right thing in getting rid of Kenny.”

Manny Machado

After 2017, the Orioles were nearing an organizational pivot. Should they try to extend their competitive window or reload for the future? Baltimore knew Machado would leave in free agency, so it explored the potential return for the 25-year-old, but didn’t find the potential return enticing

“We didn’t receive significant offers that we liked,” said former Orioles GM Dan Duquette. “The market wasn’t that robust . . . Some of the changes in the Basic Agreement made younger player contracts more valuable to the clubs. I think that was reflected in the trade market when Manny was available.”

At one point, Duquette said, the Orioles nearly consummated a trade coming out of the winter meetings, but the other team pulled its offer, and Baltimore decided the return wasn’t sufficient to make an offseason deal. The Orioles tried to win with Machado one last time.

“There is still some value to trying to win, right? That is the idea of the game, believe it or not,” Duquette said with a laugh. “My argument was that, ‘OK, we’re going to trade Manny Machado and then look around for the next 30 years for this type of equivalent talent.’ That wasn’t real attractive.”

Ultimately, the Orioles went down the drain in 2018 and ended up trading Machado to the Dodgers at the July 31 deadline for five prospects, including outfielder Yusniel Diaz (Baseball America’s No. 37 prospect after 2018). Duquette believes that the modest offseason offers for Machado serves as a case study for the limited market for young superstars entering their walk years, particularly at a time when so many teams are either committed to long rebuilds or trying to stay under the luxury-tax threshold.

Paul Goldschmidt

A year ago, the Diamondbacks had a franchise player in Paul Goldschmidt, who had just one remaining year before reaching free agency. Arizona found a market of roughly four teams for the first baseman’s services, electing to deal him to St. Louis for two projected big league regulars — catcher Carson Kelly and pitcher Luke Weaver — along with a decent prospect with a limited ceiling (Andy Young), as well as a competitive balance draft pick. They secured multiple players ready to be solid big leaguers (even if not stars) while also deepening their prospect pool.

On one hand, Goldschmidt represented a relative bargain at $14.5 million entering the final year of his deal. Moreover, at 31, he seemed open to a long-term deal with a team that traded for him.

Still, his market was limited by his position (first base) and post-prime age. One executive surmised that Betts, even with a projected salary through arbitration of more than $27 million and a near-certain entry into free agency, might find interest level to be twice that of Goldschmidt’s given his value in center or right, creating the possibility to exceed the package garnered by Arizona.

But by how much? That’s hard to say, and even harder to say whether it will exceed the value of what Betts might do for the Sox in their hopes of competing in 2020. Precedent will matter less than actual trade offers.

“So much of what a player’s market ends up being is dependent on the teams that are interested,” said Red Sox assistant GM Brian O’Halloran.

“The past is certainly something we look at, but every market is different, and we also have to weigh the importance of winning in 2020 and how any particular trade might affect that.”

Alex Speier can be reached at alex.speier@globe.com.