Nick Castellanos knew what was brewing. The Prince Fielder trade had set in motion plans that cued Castellanos for job-relocation. Which is why, on Monday of this week, Castellanos had begun taking ground balls daily during drills with his old infield coach, Rudy Pena. But not until new Tigers manager Brad Ausmus called him Wednesday did he get a stronger, liberating sense that he was returning to his old position, third base. “I think it’s gonna be a pretty smooth transition,” Castellanos said Thursday during a phone conversation from his home in Davie, Fla. “I’ve played there the longest. “I haven’t played third base in a year and-a-half, but I’m already four days into taking ground balls, and already I feel 100 times better, because I’ve done it for so long.” Castellanos, 21, has been the most entertaining story of player development in the Tigers system since he was drafted in 2010 as Detroit’s top pick. He is a 6-foot-4, 210-pound right-handed hitter who is projected by most scouts to be a middle-of-the-order slugger on the level of Rays star and third baseman Evan Longoria. But dislodging Miguel Cabrera from third base was going to be difficult when Cabrera enjoyed playing third and when Fielder was planted at first base, wrapped within a mountainous contract through 2020. Two weeks ago, Fielder was moved in a deal that sent him and his remaining $168 million in paydays to the Rangers in a swap for second baseman Ian Kinsler. It was obvious the Tigers, minus any further realignment of their infield, would return Cabrera to the position he had played during his first four seasons in Detroit, first base, which would clear space for the team’s No. 1 position prospect. The Tigers were hesitant to announce strategies, wanting to work diplomatic channels with Cabrera. Their two-time Most Valuable Player and one of the most important franchise hitters in team history deserved to sign off on yet another position shuffle. Cabrera has since said he is aboard. It freed Dave Dombrowski, the Tigers president and general manager, to say during Wednesday’s introduction of new closer Joe Nathan that Castellanos and Cabrera will be the Tigers’ probable corner infield tandem in 2014.