The Minnesota Twins have exercised their $6 million option on closer Joe Nathan. The Twins could have bought Nathan out for $1 million. But the right-hander's 160 saves and a 1.94 ERA over the past four years make his salary a bargain by market value. He turns 33 next month. Last year, Yankees' closer Mariano Rivera and Mets' closer Billy Wagner each made $10.5 million. And seven other closers made as much or more than Nathan will make next year.