We’d seen it before, so it was no real shock when Robby Hefflinger struggled in his first look at Double-A pitching. After batting .286 with 21 homers at Class A Lynchburg to start the 2013 season, Hefflinger batted .170 with six homers for the Double-A Mississippi Braves. He joined the likes of Jarrod Saltalamacchia, Josh Burrus, Van Pope, Brandon Hicks, Jordan Schafer and Cody Johnson as Atlanta prospects who arrived in Pearl with great expectations but failed to deliver — at least initially. Some (Salty, Schafer, Hicks) got past that wall and made the big leagues, some didn’t. Hefflinger’s second tour of Double-A starts tonight when the M-Braves open the 2014 campaign against Mobile at Trustmark Park. “He had some struggles here,” M-Braves manager Aaron Holbert said, “but he’s cleaned up some things in his swing.” Hefflinger said his swing adjustments primarily involved what he does with his hands: “I’ve tried to narrow myself.” This is a big year for the 6-foot-5, 235-pound outfielder, 24 and entering his sixth pro season. He is still on the Braves’ prospect chart. With 64 career homers, he is rated the organization’s best power hitter, though the TeePee can be tough on right-handed sluggers. Hefflinger said he didn’t feel overwhelmed by Double-A pitching last year. “It wasn’t too much different (from A-ball),” he said. “I was putting a lot of pressure on myself. There’s a lot of anticipation and expectations you’re trying to fill. I just started doing things mentally that made it tough on myself.” Hefflinger also struggled in the Arizona Fall League, where he said he felt a little worn down, and then took the winter off. His first at-bat of the spring — his first in some five months — was in a big league game, and he struck out. “I was thinking, this is going to be rough,” he said. But Hefflinger said he had some good at-bats in minor league games toward the end of camp and arrived in Mississippi swinging the bat well. Holbert isn’t going to pressure Hefflinger early on, putting him in the sixth spot in the lineup for opening day.