Why is Justin Turner's jersey stained

Why does Justin Turner always have a black smear on the back of his jersey? Superstition? Also, why do some players batting helmets have mud/oil rubbed on the front of them?

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Does JT Ruin Every Jersey of Every Game or What is their Laundry Department Using to Clean Them? I Need Some of That Detergent! : r/Dodgers

Justin Turner Authentic Game-Used Jersey from 5/11/21 Game vs. SEA

Dodgers Star Justin Turner Has Unusual Jersey Modification

Plaschke: Justin Turner's act of selfishness leaves stain on Dodgers' championship moment - Los Angeles Times

Men's Dodgers Black 2019 Golden Edition Justin Turner Flex Base Jersey

Leader. All-Star. World Series - Los Angeles Dodgers

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Does JT Ruin Every Jersey of Every Game or What is their Laundry Department Using to Clean Them? I Need Some of That Detergent! : r/Dodgers

Why is Justin Turner's jersey stained

Why Does Justin Turner Smear Dirt Across the Back of His Jersey? - LAmag - Culture, Food, Fashion, News & Los Angeles

Why Does Justin Turner Have a Stain on His Jersey? The Mystery, Solved

What causes the stain on the back of Justin Turner's jersey? : r/Dodgers