The idea was simple. One day out of every five, Buster Posey wouldn't be the catcher. It didn't matter if Posey was at first or resting entirely. One day out of five, someone else would be in the lineup behind the plate. Wouldn't it be awesome, then, if it were a catcher who could hit well?

That was the dream, at least. It also had another benefit: In the event of emergency, the Giants wouldn't be completely screwed. This actually came up this season, but in an unlikely way. With two broken outfielders, Brandon Belt had to shift to the outfield occasionally, putting Buster Posey at first and moving Susac behind the plate. Susac got at-bats that would have gone to Hector Sanchez, Jarrett Parker, or Ryan Lollis. This is why they didn't want to trade Susac this offseason.

We looked at this in January, back when Susac was coming off a short and valuable stretch as a rookie backup.

Susac was worth a win above replacement last year in 20 starts. If he doubles the games played, that will mean ... multiply by pi ... he could be that magical two-win backup that turns Crawford into Tulowitzki (or Hunter Pence into Jose Bautista) in an abstract way. Those two wins are almost equal to the difference between Ben Zobrist and Gregor Blanco's Steamer projections.

Well, Crawford has been more valuable than Tulowitzki, and Blanco has been more valuable than Zobrist, but you get the point. Lucking into a two-win backup catcher instead of a replacement-level catcher was almost like turning a regular into an All-Star.

There was the caveat, though.

Susac probably isn't a two-win backup catcher.

Halfway through the season, the obvious has been confirmed. Susac isn't a secret weapon. He's an average, possibly above-average, backup catcher, which is almost like a LOOGY when it comes to value. Nice to have. Not exactly a difference maker. Susac's wins above replacement on the year: 0.1.

Susac is hurt by that metric because of his defense, as he's thrown out just four runners trying to steal out of 31 attempts. His framing numbers have been average or better, so maybe he deserves a little credit for that. Still, it's reasonable to believe that his defense is a little raw, and that sitting on the bench for 60 to 80 percent of the time isn't going to help.

Which brings us back to the question from January. Is Andrew Susac worth more as a backup, or is he worth more in a trade? It's important to ask again because now we've seen what it looks like when he isn't a secret weapon, when he isn't an All-Star buried behind another All-Star. If he's a backup catcher, he's probably going to be as valuable as ... the typical backup catcher.

That means his value to the team hinges on their future plans with him. Call it the Greater Value of Andrew Susac Theorem, and it's a two-parter:

1. If the Giants have internally decided to move Buster Posey from behind the plate within the next two years, it's hard to see how they'll find a better option to replace Susac, which means he shouldn't be traded.

2. However, if the Giants are committed to using Posey as a catcher for the indefinite future, there is almost no way that Susac will be as valuable on the field for the Giants as he would be in a trade.

It's simple, now that we've gotten rid of the idea that the Giants are somehow going to carve out 300 (mostly quality) at-bats for him. There was a time when the organization wasn't sure how they were going to get Mike Aldrete at-bats on the same team as Will Clark. They experimented with Aldrete in the outfield, but eventually the point was moot: He wasn't the kind of hitter who demanded that his team plan around his talents. Clark was that kind of hitter. Posey is that kind of hitter. Susac probably isn't.

And there's almost no way the Giants have some secret plan to move Posey. There's no War Plan Red buried away in some secret dossier. Bochy dismisses the question. Posey dismisses the question. No one even pays it lip service. That means that the value of Andrew Susac's pre-arbitration years would be limited to 200 at-bats of varying quality every season, and in that time he wouldn't be allowed to develop defensively as much as he would if he were a full-timer somwhere else.

This isn't a plea to trade Susac. It's nice to have a backup catcher who could start on 10 or 15 teams around the league. The status quo has its charms. It's just a note that even though five years of a low-cost, average-or-better catcher is very valuable, the Giants might realize more value in a half-season of whatever starting pitcher he can bring back in a trade.

It doesn't just have to be a half-season of a rental at the deadline, either. The Giants can get creative in the offseason, if they want.

#Braves have let clubs know they're open to dealing from pitching prospect depth in a trade for a bat. They've asked about young catchers — Jayson Stark (@jaysonst) July 3, 2015

Pitching prospects are a fickle beast ... but so are backup catchers.

If Susac is still with the Giants in three years, I'll be stunned. It might be the master plan -- heck, I don't know -- but it'll still surprise me. He's not the magic backup to Posey that we secretly hoped, though, and I'm wondering if this is the year the Giants figure out the best way to cash in on his talent.