When the A's traded for Craig Gentry, one major reason was because of Coco Crisp's value. When Crisp was unavailable, the dropoff to the next option was the biggest gap on the team.

Exposure, the A's call it. They have advanced metrics to analyze it, and to limit it they dealt outfield prospect Michael Choice to the Rangers for super-sub outfielder Gentry.

So, who is the next most valuable player on the team in terms of trying to limit exposure? The answer isn't obvious. It's not third baseman Josh Donaldson, or left fielder Yoenis Céspedes, or one of the young starting pitchers.

According to the A's tables, it's catcher Derek Norris, who provides terrific numbers as a right-handed hitting catcher in a platoon and plays solid defense to boot. It's not easy finding someone to replace such a commodity at the big-league level, which is why Oakland traded for Kurt Suzuki when Norris was hurt last summer, and why the A's acquired Chris Gimenez this winter.

"One area we focused on is catching, because with our emphasis on versatility, at other positions, we have guys who can play a couple of positions. But you're either a catcher or you're not," said Farhan Zaidi, the A's assistant general manager/baseball operations.

"Norris is so good against left-handed pitchers. He's got close to a 1.000 OPS (.990). He's a good pitch framer. He's a good defensive catcher. If he got hurt, who could step in as the right-handed hitting catcher? It's not easy to replicate what Norris gives us."

The flip side, of course, is that the A's have a 25-year-old catcher stuck in a platoon for the third year in a row, this season with lefty-hitting John Jaso or Stephen Vogt. That might slow his development, or pigeonhole him as a part-time catcher. Norris insists he has the ability to play every day, and the A's agree - but that's not the way Oakland does things. These days, it's Platoon City.