Given time, the Red Sox still believe Will Middlebrooks will become the player with whom they were so enamored when they traded Kevin Youkilis a year ago. For now, though, Middlebrooks is regressing. And so, having already ceded the third base position to sizzling Jose Iglesias, Middlebrooks was optioned yesterday to Triple-A Pawtucket, where he’s expected to stay until he regains both his lost swing and his damaged confidence. Manager John Farrell met with Middlebrooks at about noon, and by the time most of his teammates arrived at Fenway Park for the opener of a two-game interleague series against the Rockies, the 24-year-old’s locker was empty, his baggage — including a .192 average and .228 on-base percentage, the lowest of any regular major league third baseman — on its way to the minors. “His skills haven’t gone backward. He’s still a very talented player,” Farrell said. “This isn’t uncommon for a young player. To take a step back now for the bigger picture, he’s finding his way to become a major league player.” In hindsight, perhaps the Red Sox should have seen this coming. After all, for as good as Middlebrooks looked last season in becoming the first Sox rookie to hit at least 15 homers since Ellis Burks in 1987, he had a grand total of 267 major league at-bats before being installed this season as a primary right-handed power hitter in the middle of the order. Middlebrooks’ season began promisingly enough when he hit three homers in an April 7 victory in Toronto, but he fell into a 5-for-54 slump from which he never truly emerged. There were glimpses — a game-winning, three-run double in a May 16 victory over the Rays comes to mind — but they were fleeting at best. Farrell noted that Middlebrooks’ swing changed from a “strong line-drive approach that is normal for him” to trying to get more lift on the ball. And the longer Middlebrooks went without getting hits, the more his confidence took a hit.