SAN DIEGO -- Shortly after the conclusion of the regular season, the Mets dispatched a cadre of team employees to Puerto Rico to work with Edwin Díaz. Among them were folks with expertise in nutrition, physical therapy, strength and conditioning.

Several weeks later, upon his hiring as pitching coach, Jeremy Hefner began digging into data regarding D¨ªaz's release point, body mechanics, velocity and slider break. Hefner met with bullpen coach Ricky Bones, assistant pitching coach Jeremy Accardo and pitching analyst David Lang, all of whom worked alongside D¨ªaz last season. Manager Carlos Beltr¨¢n, a former teammate of D¨ªaz's at the World Baseball Classic, also checked in with one of his most important returning players.

In concert, those people hope not only to diagnose what ailed D¨ªaz last season, when he posted a 5.59 ERA as Mets closer, but to fix it before pitchers and catchers meet on Feb. 10 in Port St. Lucie, Fla.

"We've identified some things that will help Edwin moving forward," Hefner said on Tuesday. "[I'm] looking forward to talking to him about those, and working on those things right now, and not even waiting until Spring Training, but engaging him and trying to get him down a good path right away."

Added general manager Brodie Van Wagenen: "We put a very specific action plan in place early in the offseason so that we'd have a long runway to be able to see the results."

Because the Mets appear hesitant to spend significant dollars this offseason, and because they have little prospect capital they can afford to deal away in trades, one of their surest paths to improvement would be a renaissance for D¨ªaz. Just 25 years old, Diaz is only a year removed from saving 57 games in 61 chances with the Mariners, posting a 1.96 ERA in the process. That mark mushroomed last season, to go along with seven losses, seven blown saves and 15 homers -- as many as in his previous two seasons combined.

Yet promising signs remained. Most notably, D¨ªaz struck out 99 batters in 58 innings, a rate even greater than in 2018. When the Mets acquired D¨ªaz as the centerpiece of a seven-player trade last December, they did so with the intention of having him close for years to come.

One poor season isn't going to change that, Beltr¨¢n said. It's not as if the Mets, who may shift Seth Lugo to the rotation, are overflowing with alternatives, and the free-agent market for back-end relievers is weak. For those reasons, the team intends to proceed with D¨ªaz at closer.

"There's no doubt that last year he had a down year," Beltr¨¢n said. "This year, he's working really hard and he's in great shape. So we expect him to be in that position."

The key will be correcting what ailed D¨ªaz in 2018 -- whether it was fastball command, slider break, mechanical problems, confidence issues, strength, nutrition or any combination of those things. The support system is in place. In Van Wagenen, D¨ªaz has a GM who publicly committed to him shortly after the season. In Beltr¨¢n, he has a friend, countryman and former teammate with a vested interest in his success. In Hefner, he has one of baseball's more analytically minded pitching coaches with reams of data at his disposal.

How that group recalibrates D¨ªaz may prove as important as any Winter Meetings transaction the Mets might make.

"He went through a process last year that he needed to go through," Beltr¨¢n said. "If he would have received all this good advice, maybe it would have helped him a little bit, but you've got to go through the process to understand the system and understand how things work. There's no doubt that he realizes it's a learning experience, so I believe he's going to be ready for it this year. He's super talented. What he did in Seattle is not a fluke."