Two years ago, Matt Kemp was an absolute monster for the Dodgers. He hit .324/.399/.586 (172 OPS+) with 39 home runs and 40 steals while leading NL position players in WAR (8.1). That performance earned him a second-place finish in the NL MVP voting and an eight-year, $160 million contract extension.

This year, though, Kemp is hitting just .261/.313/.344 (86 OPS+) with two homers and seven steals in 47 games. He has been below replacement level at -0.1 WAR according to Baseball-Reference, meaning Los Angeles could get more out of a spare Quad-A outfielder that teams typically have stashed in the minors.

There's reason to believe Kemp's struggles are just physical, however, specifically having to do with his left shoulder. He had surgery in October to repair a detached labrum in the shoulder after suffering the injury crashing into a wall and playing through it in the second half. Kemp insists he's healthy, but on Friday manager Don Mattingly hinted that might not be the case.

“I noticed his swing getting cut off, but nobody's said anything medically that his shoulder is tight,” said Mattingly to Steve Dilbeck of the Los Angeles Times. “When his swing is good, it's center field, right-center. He still topspins the ball to left field and always has ... If he's topspinning 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, but not that much.”

In a piece of Baseball Analytics, Peter Gammons wrote about the importance of the lead shoulder and how hitters can lose power and effectiveness following injuries. Adrian Gonzalez and Jacoby Ellsbury are two more examples.