Here's a picture of Piazza hitting the "record-tying" home run:
I wrote about this last April. Here's what I said back then:
The answer to the all-time leader in home runs by a catcher comes from Chuck Rosciam of the Encycolpedia of Catchers, but it's not at straightforward as I expected. Chuck explains that Fisk holds the "record" according to the SABR HR Encyclopedia at 351, but...
Fisk apparently holds the Record with 351 (out of 376 hit), BUT five of those non-catcher ones were hit between/during position changes. That is, Fisk's last defensive position was catcher in a game, then he came to bat and hit a HR and then he took up a different position in the bottom of the same inning. My logic tells me that he was still a catcher and that he didn't change positions until after he hit those five. That would make his Catcher-only total 356. However, there are 3 games in which he started as a non-catcher, then changed positions during the game with a HR being hit between changes (same rule as previous) and was WRONGLY CREDITED with a homer as a catcher. Now subtract 3 from 356 to make his Catcher Total = 353. Piazza's HR's as a catcher I believe stand at 342 unless he hit one in the past two days. That means that he needs 13 more to hold the record, which he will easily do plus some this season.
It gets kind of complicated. Besides as Chuck mentions, Piazza will obliterate the old "record" anyway, barring some catastrophe. So it won't matter by the time he retires if they count the home runs he hit just as a catcher or they count them all. He will still rank number one among all catchers.
Piazza only played 68 games in 2003, so he never did have the opportunity to set the new "record".
However, what I find interesting is that so many sports news services carried the news as if the record were kept officially. The record is something derived by baseball scholars using subjective (and I believe incorrect) assumptions.
If we use Chuck's value of 353, which is more based in basic baseball scoring—not to mention the old schoolyard rule that you have to play the field before you bat—Piazza is still dingers shy of the record. Of course, Piazza should go on to obliterate the record. But keep in mind his age, recent health issues, and the Mets' desire to move him to first. Let's say that the Mets and Piazza agree on a move to commence after his next home run. Piazza would then own the record and the Mets would be happy. However, in thirty years when some scholar redresses this error, Piazza will fall one home run short. And the long-retired Piazza will have to give back his secret decoder ring or whatever they give him for breaking the record. Let's just hope that Mike hits a bunch more before the inevitable transition to first base becomes fact.