Don Mattingly says shoulder is hampering Matt Kemp’s swing

Matt Kemp’s surgically repaired left shoulder is hampering his swing and Dodgers Manager Don Mattingly said Friday that has played a big part in Kemp’s season-long struggles at the plate.

Kemp, who is hitting .266 with two home runs and 17 runs batted in, cannot fully extend on his swing, something teammates Adrian Gonzalez and Hanley Ramirez both experienced when they returned from shoulder surgery.

“He’s not where he wants to be. He’s frustrated out there,” Mattingly said of Kemp. “The biggest thing we want to do with Matt is try to keep the bat in the strike zone longer. Just from my standpoint of watching Matt the year before and this year, when he’s going good he’s driving the ball to center field, right-center.”

BOX SCORE: Cardinals 7, Dodgers 0

Kemp’s frustration was obvious during early batting practice Friday when stormed out of the cage, snapped a bat over his knee and stomped into the clubhouse, where he declined to blame his struggles on his shoulder.

“I don’t really want to talk about hitting right now,” he said. “I’m good. I’m just figuring out some things.”

Mattingly, however, insisted Kemp’s shoulder is still tight.

“I noticed his swing getting cut off,” he said. “To me the key is, is he top-spinning [the ball] into left-center or is he top-spinning the ball to short? That’s two different things.

“If he’s top-spinning in left-center and left field, it tells me he’s getting extension to a certain point and he’s cutting off just a little bit.”

Team President Stan Kasten said the solution may not be that simple.

“It’s not one thing. If it was one thing, we’d fix it,” he said. “We won’t be as good as we can be until Matt Kemp returns to being the real Matt Kemp.”

Healthy Hanley

Ramirez, whose return from right thumb surgery lasted less than a week before he returned to the disabled list with a strained left hamstring, is eager to get back on the field again but the Dodgers are urging caution with the shortstop.

“He told me he was going to be ready today. So I am trying to hold him back a little because I know that he’s not ready yet,” Mattingly said.

Ramirez is participating in pregame drills and expects to begin running the bases Saturday. But he is likely a week or more away from a minor league rehabilitation assignment.

“It’s almost June and I’ve only played four games. That’s never happened in my career,” Ramirez said. “It’s a disappointment and I’m trying everything that I can to stay healthier. But I just have to stay mentally stronger and keep working and try to get back.”

Short hops

Jerry Hairston Jr. (left groin strain) played six innings at third base for Class-A Rancho Cucamonga on Friday, going 0 for 3. He is expected to play six innings again Saturday and if there are no setbacks, he could rejoin the Dodgers . ... Left-hander Scott Elbert (left elbow surgery) will make appearances Saturday and Sunday for double-A Chattanooga and could be activated as early as next week.

kevin.baxter@latimes.com

Twitter: @kbaxter11