Starling Marte leads the Majors with a .321 batting average.

Starling Marte will not win a batting title this year.

Wait, what? Let us explain. It’s one of baseball’s most fascinating record-keeping quirks, and it involves a fun history lesson, too.

Marte's situation

Marte indeed leads in batting average, entering Friday four points ahead of Vladimir Guerrero Jr. and Trea Turner, both at .317. But Marte is ineligible for a batting title because, despite being a qualified hitter overall -- having amassed at least 3.1 plate appearances per team game -- he won’t qualify in either league alone.

To win the AL batting title, a player must reach 502 plate appearances (that’s 3.1 times 162, for a normal-length season) while in an AL uniform. To win in the NL, a player must reach that mark in an NL uniform. And while we recognize which batter leads the Majors overall each year, there isn’t a specific MLB batting title. A batter must qualify in a specific league in order to win a batting title.

Marte, of course, was traded on July 28 from the Marlins to the A’s for Jesús Luzardo. At the point when he was traded, he’d hit .305 in 275 plate appearances as an NL player. He wasn’t in the batting title conversation, for two reasons: Nick Castellanos led the NL, at .329, and Marte wasn’t even a qualified NL player at that point, due to injury time missed.

But since he’s joined the A’s, Marte has hit .343 in 191 plate appearances, which has done two things: gotten him back into the qualified players list overall, with 466 PA in the A’s 146 games, and also raised his overall season average to .321, skyrocketing him to the top of the list. Now, Marte is atop that overall batting leaderboard, because he is a qualified player, MLB-wide, even though he isn’t qualified in the AL or NL alone.

Again, it’s important to note that this quirk applies only because Marte was traded across leagues. If he’d gone from the Marlins to the Cardinals, or any other NL team, he’d be a qualified NL player at this point, if he had the same exact stats that he has today.

This means that, if the season ended today, or at any point in this current order, Marte would be your 2021 leader in batting average in MLB, but he would not win a batting title. That’s important in relation to Guerrero, too: Marte’s batting average cannot preclude Guerrero from winning the AL batting title -- as it currently stands, Guerrero would win it, in his quest for the Triple Crown. But Marte does stand in the way of Guerrero becoming the first player since Mickey Mantle in 1956 to lead all players in all three Triple Crown categories, since he’s qualified overall.

Has this happened before?

Marte wouldn’t be the first player to lead the Majors in batting average and not win a batting title. Here’s where the history lesson comes in. He’d be the second player in the Modern Era (since 1900) to find himself in that spot, joining Eddie Murray in 1990.

Murray, unlike Marte, didn’t change teams, but instead lost out on a batting title because another player changed teams. Here’s what happened.

Murray hit .330 for the Dodgers, finishing a point ahead of the Royals’ George Brett for the MLB lead. Brett won the AL batting title. But Murray finished five points behind another player for the NL batting title -- despite leading the Majors overall.

Enter: Willie McGee. He hit .335 in 542 plate appearances for the Cardinals, through Aug. 29. That day, like Marte, he was traded to the A’s, with whom he finished up the season. He hit .274 in 123 plate appearances in Oakland, finishing with a .324 average overall.

But since he was traded across leagues, that .335 average in the NL froze the moment he put on an A’s uniform. And since he was traded in August and had accumulated enough plate appearances to be qualified at the end of the season, he led the NL in batting average and won the batting title -- despite finishing the season in an A’s uniform, and with an overall batting average below Murray’s .330.

What about his stolen base totals?

While rate stats involve qualifying, as noted above, there’s more potential history with Marte’s cross-league stats if we look at counting figures -- namely, his stolen base totals. Overall, he leads MLB with 45, five more than Whit Merrifield and 16 more than Turner.

But if we break it down by league, it gets fascinating. His 23 stolen bases with the A’s are tied for fourth in the AL. And his 22 with the Marlins before the trade? That figure still ranks fourth in the NL.

No player has ever finished even in the top 10 in stolen bases in both the AL and NL in the same season, according to the Elias Sports Bureau. And Marte could be top five in each.

The researchers at Elias were kind enough to dig through other "whole number" stats -- hits, doubles, strikeouts and so on -- to see if anyone had ever finished in the top 10 in both leagues in any of them. The only one they could find was complete games by pitchers.

In 2009, Cliff Lee was tied for fifth in the AL in CGs with the Indians and tied for third in the NL with the Phillies, who acquired him in late July. The year before, CC Sabathia led the NL in complete games with the Brewers after they traded for him, and he was tied for third in the AL with the Indians. In 2002, Bartolo Colon finished tied for fourth in the AL in complete games with the Indians and was tied for fifth in the NL with the Expos after a trade. And in 1998, Randy Johnson finished tied for eighth in the NL in complete games with the Astros after a trade, and his AL total with the Mariners beforehand was tied for fifth.

There’s some precedent for this concept, but not very much. And that’s pretty much the story of Marte’s season: In addition to chasing a postseason spot, he's chasing the chance at a few unique records and marks.