The New York Mets inking right-hander Dellin Betances to a one-year deal on Christmas Eve — adding the 31-year-old flamethrower to their already well-stocked stable of high-quality arms — has given New York’s 2020 relief corps a significant shot in the arm.

According to FanGraphs and noted by Matt Kelly of MLB.com, the Mets’ bullpen is projected to lead the National League in wins above replacement (5.0 fWAR) and rank third in baseball behind Tampa Bay (5.3) and the Yankees (5.2).

The addition of Betances has increased the talent quotient in Queens to the point that he, Seth Lugo, Edwin Diaz, Jeurys Familia, and Justin Wilson are being considered one of the strongest bullpens in baseball. And justifiably so.

Though, for things to work out as projected, the Mets need two of their most important relief arms in Diaz and Familia to bounce back after respective disastrous 2019 campaigns.

Diaz, 25, for all of his issues last season (5.59 ERA, MLB-most 15 home runs allowed) has already received a strong vote of confidence from Mets manager Carlos Beltran, who expects Diaz to be the team’s closer next season.

Elite stuff, as Diaz most certainly has, will produce strikeouts — 99 over 58 innings, to be exact. But when a pitcher’s barrel rate jumps from 3.8 percent to 10.1 percent in one season — as it did from 2018 to 2019 — there’s obviously more to address than simple mechanics adjustments.

Hopefully, new Mets pitching coach Jeremy Hefner, along with assistant pitching coach Jeremy Accardo, have a course of action in place to rectify whatever caused his 2019 drop-off, as well as Familia’s (5.70 ERA, 6.30 walks per nine innings). Hefner and Accardo — two noted analytics aficionados — applying their data could generate quite the turnaround for both beleaguered righties.

Diaz and Familia returning to prominence would considerably increase the Mets’ odds of living up to the lofty hype that Betances and his demoralizing arsenal (.200 batting average against/.309 slugging against versus his curve in 2018; .170 BAA/.074 SLGA versus his slider) brings to this group.

Along with Lugo and Wilson, depth arms in Brad Brach and Robert Gsellman, and left-hander Daniel Zamora (oh, that slider…), and right-handed prospect David Peterson waiting in the wings, the Mets appear to have a viable plan for shoring up, arguably, their ultimate undoing last season. If only they showed this type of dedication to improving defense. Alas…

Of course, adding a guy like Will Harris — or even Craig Stammen or Steve Cishek, as Rob Piersall of MetsMerized suggested over the weekend —  couldn’t hurt the cause, either. In fact, if general manager Brodie Van Wagenen learned anything from last year’s relief follies, quality bullpen depth is a priceless commodity and is the last area of need that should be skimped on.