Alex Rodriguez will arrive at spring training intent on being the Yankees' regular third baseman this season, a person familiar with his thinking said Thursday. Rodriguez was undeterred, the source said, by the signing of Chase Headley to a four-year, $52-million contract to play the position Rodriguez occupied before his year-long suspension resulting from Major League Baseball's Biogenesis investigation. "Alex's mind is that job's not Headley's, it's Alex's to lose," the source said. "That's what he thinks. Alex is going into training camp thinking that he is the starting third baseman, that if there's a competition, Headley's got to win it from him. It doesn't matter about the money, what they signed Headley for. This guy [Rodriguez] can play." Rodriguez, who will turn 40 in July, has three years and $61 million left on his contract.