There is little risk in the Phillies assuming that J.T. Realmuto of 2021 will resemble the player they watched in 2019 and 2020. He has caught nearly three-fourths of their games since arriving two years ago, has outpaced his fellow catchers in most offensive and defensive categories, and has earned the right to be called the best catcher in baseball.

But the five-year contract Realmuto signed last week — which was discussed Monday in a news conference — said more about the Phillies’ belief about how Realmuto will age into his 30s than it does about how they expect him to perform this summer.

The $115.5 million contract made Realmuto the highest-paid catcher in baseball history on a per-year basis. And it’s a bet by the Phillies that Realmuto will not age like a typical catcher.

“J.T. is a little bit of a freak of nature,” manager Joe Girardi said, “because he’s such a great athlete and you don’t necessarily see such great athletes there. And that’s a special commodity. He’s a special commodity that we have and I just look forward to watching him work the next five years because it’s fun to watch.”

No catcher over the last four seasons has caught more innings than Realmuto and only two Phillies — Bryce Harper and Rhys Hoskins — have started more games than Realmuto since he joined the team in February 2019. The catcher tried to play nearly every day, fighting to keep himself in the lineup whenever Girardi or his predecessor, Gabe Kapler, suggested a day off.

Realmuto has matched that workload by generating the highest WAR among catchers and throwing out the most runners over the last four seasons, and tying for the lead among National League catchers in home runs since coming to Philadelphia.

There is a case to be made that Realmuto is the team’s most important player. But a challenge to his production could be coming. Realmuto turns 30 in March, reaching an age when catchers generally see a decline in their production.

The Phillies are counting on their “freak of nature” to be different.

“We talked about our confidence in J.T. being able to be a really productive catcher for a long time, and that’s just not like a hunch,” general manager Sam Fuld said. “That’s based on what we’ve seen from J.T. on a day-to-day basis. I mean, it’s commitment. What you guys see between the lines is incredible stuff. But what you see outside the lines is, I would say, just as impressive.”

“His commitment in the weight room. Talking to our nutritionist Alexa Scully last night and she’s like, ‘I’m so excited J.T. is coming back. He’s so committed. He’s a model citizen and he’s committed to being as good as he can for as long as he can.’ Those kinds of players and teammates, they don’t grow on trees. It makes us feel a little extra confident that he’s going to be really good for a long time.”

Realmuto’s contract will take him through his age 34 season. Just 11 catchers in the last 40 years have averaged three Wins Above Replacement between their age 30-34 seasons. Realmuto averaged 4.5 WAR from 2017 to 2019 before totaling 1.4 in 2020′s truncated season.

Since 2000, 52 catchers between the ages of 30 and 34 have totaled 1,000 plate appearances. But only six of them — Mike Piazza, Jorge Posada, Javy Lopez, Ivan Rodriguez, Jason Varitek, and Carlos Ruiz — generated an OPS better than .800. Realmuto has averaged an .825 OPS over the last three seasons.

In the last 10 years, just eight catchers 30 or older have caught three-fourths of their team’s games in a season. And only two of those catchers — Yasmani Grandal in 2019 and Yadier Molina in 2013 — have matched that workload with an OPS better than .788.

“If you have quality performers, their aging process is a little bit different than others,” said Dave Dombrowski, the Phillies’ president of baseball operations. “He’s a quality performer. He’s athletic. He’s talented in that regard. He’s hardworking. So all of those things you would indicate to try to look at longevity would project into what J.T. has. So we think we’re in a position where, sure, maybe at 35 you’re not the same at 34 or the same at 30. But when you start falling off a little bit from where he is starting from up above to where it would be, we look at that as being a quality big-league performer at that time.”

Realmuto has caught the 10th-highest total of games among active catchers and it could be difficult to maintain both his production and workload as he enters the later stages of his contract. But Realmuto is confident, just like the Phillies are, that he is different.

He was a shortstop in high school before the Marlins moved him to catcher. He was his high school’s star quarterback and comes from a family of Olympic wrestling champions. Perhaps his athleticism — which he displays regularly behind the plate — could be what keeps him going well into his 30s.

“As long as I continue to work hard and continue to keep my body in shape and continue to come into the season as ready as I can, I don’t see why I wouldn’t be able to last a little longer than other catchers,” Realmuto said. “Athletically, I’m a little more advanced than most catchers are. Not all, obviously. So I feel like that gives me an edge, to where even if I decline a little bit athletically, I’ll still be ahead of the game as far as most catchers are concerned.”