FORT MYERS, FLA. - At first glance, the Twins' signing of Joe Nathan to one of the richest contracts in franchise history seems puzzling.

The team is paying about $12 million a year for Nathan to pitch about 70 innings a year. Simple math would indicate that paying Torii Hunter $18 million a year for 150 games, or Johan Santana $23 million a year for 220 innings, would make more sense.

The Twins are locking up Nathan for four years (at $47 million, guaranteed) even though this year, and perhaps next, could be rebuilding seasons, when a closer might not make much difference in the team's fortunes. Couldn't the Twins have spent this money more wisely?

Actually, no.

While $47 million is a lot of money for a team with a target payroll of about $70 million, the Twins are ...

• Under payroll this season, and are wiser investing that money in Nathan than banking it or hoping they will ever sign someone of Nathan's caliber in free agency.

• Getting an elite closer for a little more annually than the Reds are paying Francisco Cordero and less than the Yankees are paying Mariano Rivera on his retirement tour.

• Locking up one of the players they consider vital to their future and their clubhouse through the opening of the new stadium.

• Signing a player who they believe still will be effective at the end of the contract, whereas Hunter and Santana wanted deals that their new teams might regret in three or four years.

• Don't have enough elite players to allow any more to leave.

When the Twins traded Luis Castillo last year at the trading deadline, it appeared the Pohlads were more interested in saving a few million than giving that team every chance to contend. When Hunter, Santana and Silva left in free agency, you could have surmised that the Pohlads were operating on the cheap.

In reality, the Twins' front office could have handled the Hunter and Santana sagas better, but the Pohlads have invested heavily in this roster.

Joe Mauer is signed through 2010 (four years, $33 million), and there is little doubt the Twins will sign him to another long-term deal. Justin Morneau is signed through 2013 (six years, $80 million).

Michael Cuddyer is signed through 2010 (three years, $24 million). Nathan is signed through at least 2011, with a team option for 2012.

The Twins also made offers of four years and $80 million to Santana, and three years and $45 million for Hunter.

Even without those two, the Twins have invested $184 million in four key players who should be in Twins uniforms on Opening Day 2010. Consider that Carlos Gomez and Delmon Young will be under Twins' control for six and five more years, respectively, and the core of a future contender is in place.

"I get excited, thinking about that," Morneau said. "I get to play with these guys for a long time. We're going to have Gomez, Young, Cuddy, Joe, and now Nathan. That's a big move for us.

"I want Joe [Mauer] to sign a six-year contract, and then I'll sign another one, and we'll both be here until we're 45."

The Twins should have been more proactive with both Hunter and Santana, either signing them to extensions well before they started gravitating toward free agency, or taking the drastic and unpopular measure of trading them before their last year in Twins uniforms.

With Nathan, another elite player, they are avoiding those pitfalls, keeping one of the best closers in the game at what, in the ever-inflating world of baseball contracts, is a reasonable price that could quickly become a bargain.

Perhaps the most important aspect of this deal is that they didn't give Nathan a full no-trade clause. If the Twins find the need to trade him, few contending teams would balk at acquiring this contract.

The Twins have been saying for months that Nathan was a priority because they have no other closers in the organization, and they believe Nathan's dominance and durability have enabled them to field one of baseball's best bullpens since he arrived in 2004. All true.

This contract represents, at least, a good investment. And if Nathan is closing for a contender in the new ballpark in 2010, it should be viewed as a shrewd move, and the latest proof that the Pohlads intend to win.

Jim Souhan can be heard Sundays from 10 a.m.-noon on AM-1500 KSTP. • jsouhan@startribune.com