What an exercise in elasticity it was to talk about Jhonny Peralta these past three years. You had to stretch and twist and contort to satisfactorily explain the contradictory nature of his performance as one of the most important Tigers in manager Jim Leyland’s lineup. On one hand he was irreplaceable. Shortstop is a baseball field’s nerve center. And in trotting onto that infield dirt every day for every game ready to play even when Leyland insisted on awarding him a day off he was as reliable as the Mackinac Bridge. He gobbled up ground balls hit within his narrow radius. He smoothly made on-track throws to first base even if they never threatened the speed limit. And during most seasons he got his share of big hits slammed a few home runs all while displaying the most consistently saintly disposition of any infielder this side of Ramon Santiago. He was a steal — one of Dave Dombrowski’s best-ever trades brought to Detroit three summers ago from Cleveland for the paltry price of a fringe pitcher who never has cracked the big leagues. But he also had a flip side that showed up during a few too many games. Peralta had been moved from shortstop to third base by the Indians. It was evident in Cleveland and later in Detroit why the transfer had been necessary and why the Indians parted with him for a song. Peralta never touched scores of ground balls that slithered into the outfield for base hits. He has had particular trouble moving to his left snatching bounders up the middle that wider-ranging shortstops often snag. He was better at going into the hole between shortstop and third. But when he did slurp up a deep grounder there his arm although accurate lacked the steam necessary to make a play so many shortstops pull off. But the Tigers lived with his shortcomings these past 37 months gratefully all because he was so trustworthy. Until that is Monday when Commissioner Bud Selig’s office announced Peralta would be suspended 50 games for his part in an investigation tying Peralta to performance-enhancing drugs dispensed by a shady Miami-area strip-mall dispensary known as Biogenesis. Peralta did not contest the suspension. A man who had consistently denied any involvement was left Monday to admit: “I made a terrible mistake that I deeply regret.”