There is one burning question all Giants fans are asking this offseason: Why haven’t they re-signed Buster Posey to a long-term deal?

The answer: It’s complicated.

What could be so complicated, you ask, about re-signing the reigning NL MVP and batting champ and the guy that’s caught the last pitch of not one, but two World Series.

Well, consider that no player with so little MLB service time has accomplished so much. As ESPN’s Buster Olney writes, Posey hasn’t even played two season’s worth of MLB games (he’s only played in 308 career games).

Despite having not played three full seasons, Posey qualifies for arbitration a year early because he is what MLB considers a “Super Two.” He’s played less than three years, but more than two and ranks within the top 22% of all two-year players with the most service time.

According to Baseball-Reference.com, Posey has 2.161 years of service time. Fox News reports that the cutoff to be considered Super Two was 2.139. So 2013, which should have been a year in which the Giants can determine his salary, morphs into a bonus arbitration year for Posey. That means Posey can negotiate his 2013 salary with the Giants.

Or, the Giants and Posey can come together and work out an extension that buys out any number of those arbitration years — all, if they want — and potentially some free agent years.

While it may be complicated, the Giants front office has some pretty smart people and they need to get a Posey extension done sooner rather than later.

The Giants shouldn’t waste time going through arbitration with Posey, who turns 26 years old just before Opening Day 2013. While he’s not a free agent until after 2016, he’s approaching his prime years and the Giants would be better served paying Posey the big bucks for his late 20’s than his mid-30’s.

The longer the Giants wait, the more years they will be paying for on the back end.

Olney writes about the possibility the Giants might give Posey a rare 10-year deal. If they do that between now and Opening Day, they’ll be locking up Posey through the age of 35. Posey is a great player, but I think we can all agree that he won’t be the same player in 2022.

@Buster_ESPN Ten-year deal for Posey would surprise me. #sfgiants gun shy on long-term deals since Zito, Rowand, tho Posey a different case. — Henry Schulman (@hankschulman) January 6, 2013

If there is a player that everyone feels could live up to a 10-year deal, it’s Posey. I think the smarter deal, though, would be in the five- to seven-year range. Locking up Posey through the age of 32 is much safer. At that point, they can see if they want to venture down the road of keeping a pricey catcher in his mid-30’s.

In November, The Chronicle’s Henry Schulman wrote GM Brian Sabean said an extension for Posey was a no-brainer:

“We’ve visited it internally. We are open to the idea. He certainly deserves that consideration.”

Last April, the Giants bought out Madison Bumgarner’s arbitration years plus his first year of free agency by signing him to a five-year deal. The deal includes two option years at the end. If he and the Giants exercise both options, he will become a free agent at the age of 30. They’ve essentially locked him up for seven years.

That’s something that the Giants should do with Posey. He will make considerably more per season than Bumgarner, though.

For a starting point, when Minnesota Twins catcher Joe Mauer was up for arbitration for the first time after the 2006 season, the Twins gave him a four-year, $33 million deal instead, buying out his last three years of arbitration and first year of free agency.

Mauer was coming off his a batting title. During that contract, he won two more batting titles and claimed the 2009 AL MVP award. When that contract expired after the 2010 season, they gave their MVP catcher to an eight-year, $184 million deal prior to the 2011 season.

That’s $23 million per season. The Twins gave that contract to Mauer just before his 28th birthday. He’s locked in at $23 million a season until he’s 35 years old.

Mauer can still hit, but he’s already aging, but he’s playing less and less at catcher. I bet some in the Twins organization wish they had given him that eight-year deal sooner.

The Giants need to avoid waiting, so they aren’t on the hook for $20+ million for a mid-30’s catcher-first baseman like the Twins will be in a few years.

The Giants are committed to keeping their young core together, as evidenced by the deals given to Bumgarner, Matt Cain and Pablo Sandoval in the last few years. Needless to say, Posey is next to get a deal.

If the Giants are smart, they’ll lock up Posey soon — before he wins another MVP and jacks up his price even higher.