The return of Brett Gardner adds a dimension to the Yankees lineup. He also creates a conundrum for their defensive configuration. Gardner — pesky at the plate, speedy on the bases, rangy in the field — represents a quite useful player for this aging team. But the trouble is figuring out where to play him. With the Grapefruit League beginning this weekend, manager Joe Girardi faces something of a deadline in deciding whether to use Gardner or Curtis Granderson as his starting center fielder. He has said if the team made a switch — Garner has mostly played left field since Granderson arrived in 2010 — they must do so early in the spring. Defense metrics, like Ultimate Zone Rating, suggest Gardner is a much more accomplished fielder than Granderson. But Girardi has mentioned a series of reasons for not making the switch: Gardner missed nearly all of last year due to elbow surgery. The sizable expanse of left field at Yankee Stadium makes covering the territory more important than in most parks. Plus, Girardi does not want to hamper Granderson’s approach at the plate by forcing him to learn a new position. He reminded reporters that despite all the hand-wringing about Granderson’s batting average (a career-low .232) and strikeouts (a career-high 195) last season, Granderson still hit 43 homers and drove in 106 runs.