MIAMI — Marlins rookie catcher Joe Mack has emerged as one of the most productive backstops in baseball since his Major League debut on May 4, ranking first in the National League in fielding run value (8), first in the Majors in runners caught stealing (19) and third in fWAR (1.9) among primary catchers through his first 74 big league games.

The 23-year-old’s impact has not gone unnoticed by the coaching staff, which is now carefully calibrating his workload as Miami eyes the National League Wild Card picture. Manager McCullough said the club is balancing Mack’s production against the long-term toll of catching nearly every day.

“What Joe has brought, we’ve seen it,” McCullough said. “We’ve seen how our team has been elevated and how we’ve played, how we’ve pitched since Joe has been up here, and I don’t think that’s [a] coincidence. He’s been phenomenal.”

Mack started 38 of 47 team games — 81 percent — to open his career, a significant jump from his schedule at Triple-A Jacksonville, where he typically played two games on followed by two days off with occasional designated hitter appearances. Since the trade deadline, he has started six of nine games as the Marlins dial back his workload.

“It’s obviously a lot more,” Mack said. “Just making sure that I’m ready for each day. … Even when I’m not playing, there’s a chance for you to get in there. So making sure that I’m ready and able to give my best effort when I go in, I think that’s a task in itself, alongside the amount of days I’ve been catching behind the plate.”

Mack has focused on recovery, hydration, nutrition and 8-10 hours of sleep per night to sustain the grind. He arrived at Spring Training at 210 pounds but has watched his weight drop to 201 and even 195 in previous seasons — a pattern he is working to correct.

“It’s weird because for the last two years, I’ve played well at a lower weight,” Mack said. “Obviously, it’s a lot better when I’m a higher weight because I can use less effort and still have the same amount of power, speed, all that stuff that I’m trying to achieve. I definitely notice it a little bit.”

McCullough said the club will continue to manage Mack on a series-by-series basis. “Joe is recovering well,” McCullough said. “He’s feeling strong. He’s young, too, so I think we have that on our side. He’s still a young man. He probably could catch every game right now, but we know there’s a tax he’ll end up paying on that.”

Catching coach Craig Driver said Mack’s consistency on both sides of the ball has been unusual for a player his age. “He’s generally handled both the offensive and defensive side pretty consistently throughout the course of the workload,” Driver said. “With a lot of younger catchers, you see their catching’s fine and their offense really starts to falter when they catch too much, or they’re still hitting but they’re not catching as well as they need to catch.”

If the Marlins remain in contention for a Wild Card berth, Mack figures to stay in the lineup on a near-daily basis through the final weeks of the regular season.