This offseason began with many in the baseball world -- insiders and fans alike -- assuming that the Mets and Phillies would be scrapping it out for top-of-the-class free-agent catcher J.T. Realmuto until the bitter end.

Except, it didn't turn out the way. Instead, the Mets seemed more focused on fellow free agent James McCann -- right up until sources told MLB.com's Mark Feinsand and Jon Paul Morosi on Saturday that they had reached an agreement on a four-year deal (the club has not officially announced). Again, this might have surprised us if we had learned right after the Dodgers recorded the final out of the World Series that McCann -- a player who was non-tendered by the cellar-dwelling Tigers just two years ago -- would generate a strong market and ultimately put on a Mets uniform before the Amazin's and new owner Steve Cohen had even really pursued Realmuto.

But besides the fact that McCann's roughly $40 million deal is likely to be much cheaper than what Realmuto will command (and perhaps gives the Mets flexibility to chase other top-tier free agents like Trevor Bauer and George Springer), there were several reasons why McCann was so sought after. First, in a catching landscape short on hitters, McCann’s bat alone would be enough to garner plenty of looks this winter. Never much of a threat over his first five seasons, his offense came alive after he signed with the White Sox prior to 2019: he’s been a top-five offensive backstop since then, and actually pretty comparable with Realmuto.

McCann, since 2019: .276/.334/.474, 116 wRC+, 25 HR, 75 RBI
Realmuto, since 2019: .273/.333/.492, 112 wRC+, 36 HR, 115 RBI

Realmuto does way more than hit, of course, and no one will argue his top-prize status. But another part of McCann's game might have helped to drive up interest: his glove. Much like his offense, McCann’s résumé behind the plate was largely forgettable … right up until 2020, when it was time for him to leave the best impression on the market. His framing improvement might be the secret reason why teams were paying attention.

The turnaround

Last winter wasn’t the first reported time that McCann worked on his pitch framing, but the public data said there was still plenty of tinkering to do. He was a below-average receiver in each of his first five full seasons, per Statcast’s metrics, including a career-worst -15 runs from extra strikes total that put him dead last among catchers in 2019. But not only did those same metrics paint McCann as an above-average framer in ‘20, he was actually a top-10 performer.

McCann’s Statcast runs from extra strikes total and MLB ranks, 2015-20
2015: -14 (55th of 56 qualified catchers)
2016: -3 (44th of 63)
2017: -11 (59th of 62)
2018: -1 (30th of 60)
2019: -15 (64th of 64)
2020: +2 (T-6th of 62)

Baseball Prospectus’ (FRAA) and Sports Info Solutions’ (rSZ) framing metrics backed Statcast, which identified that McCann, one of MLB’s tallest catchers at 6-foot-3, struggled most at presenting pitches at the bottom of the zone. As The Athletic’s James Fegan detailed in January (subscription required), McCann attacked the problem by calling Jerry Narron, a former big league catcher who’s gone on to tutor standout framers like Jonathan Lucroy, Jeff Mathis and Martín Maldonado, who sent Narron his 2017 Gold Glove Award out of appreciation.

“Up to this point in my career, I’ve never really had anyone who was able to explain to me why the scoring worked the way that it did as far as the framing metrics go and how to improve,” McCann told The Athletic. “I’ll definitely be monitoring it closer than I ever have.”

The data backs the work McCann put in. A scan through his hot and cold zones on Baseball Savant quickly identifies that he made up huge ground at the bottom edge of the zone in 2020, actually ranking just outside the top five catchers in getting extra strikes in the bottom-middle area.

McCann’s framing really stood out during Lucas Giolito’s no-hitter when, according to Sports Info Solutions’ Mark Simon, McCann got four strike calls on pitches that had less than a 50% strike probability. You can see some of his best work in that game here:

One can imagine how crucial it was to steal lower-edge strikes for Giolito’s off-the-table changeup, Dallas Keuchel’s tantalizing slider and Alex Colomé's burrowing cutter. And while catcher ERA is far from a perfect stat, 2020 White Sox pitchers did finish with a 2.82 ERA with McCann behind the plate.

Here’s what you might (and should) be thinking: we’re only talking about one year of improvement -- and indeed, McCann started only 27 games at catcher while sharing time with Yasmani Grandal. It’s an extremely small sample. But McCann’s timing, as a 30-year-old catcher set to hit the market, couldn’t have been better. Perhaps the Mets, on top of the financial considerations, bought into the same late-bloomer narrative with McCann's glove that accompanies his offense.