If he hadn't signed a contract extension in November, Gary Sheffield would have become a free agent in six weeks. Sheffield said Friday he hasn't thought about the options he would have had, and there's a simple explanation for that. "I'm very happy," he said, before the Tigers opened a three-game series against the Minnesota Twins. "I couldn't have made a better choice." Sheffield signed a two-year, $28-million extension when the Tigers acquired him from the Yankees after last season. He reiterated Friday that he expects this to be his final contract. He believes he will be able to manage the pain in his right shoulder well enough to play through 2009. The shoulder has not required a third cortisone shot this year. "I've shown myself that I can get it back to where it needs to be, so I can be the player I'm capable of being," Sheffield said. "That's encouraging. I'm always willing to put in the work. I don't like playing mediocre."