Johnson is hitting .273, but he has struck out 20 times in 66 at-bats.
"When they've thrown the ball over the plate, he's put pretty good swings on it," Barnett said. "There really isn't anything mechanically wrong in his swing. He had a great Spring Training and swung the bat very well, and that's a credit to his swing. In Spring Training, pitchers are trying to get ready and they're going to throw more strikes."
What Johnson is dealing with now is a lack of good pitches to hit, as clubs who have noticed he'll chase pitches out of the zone have quit throwing him strikes for the most part.
"When I do get a pitch to it, I hit it pretty good," Johnson said. "I got here early [Tuesday], and that's something I'm going to try to focus on is pitch selection. I'm going to get better with it."
Johnson has been going to the bullpen to track pitches when the starters have been throwing on the side. He's also gone down in the cage and tracked pitches off a pitching machine that throws breaking balls.
"Pitch selection is huge at this level," Barnett said. "If they know you're going to chase, they're not going to give you anything to hit. He's aware of it, and we've talked about it at length. He's bound and determined to make the adjustments."