MLB Stars: Goin' Customizing Crazy ... For The Xmas Season

You might not think the MLB is the swaggiest league around ... but it turns out the hardball heroes are going custom car crazy for the holidays ... and TMZ Sports has pics of the jaw dropping rides.

We spoke with Alex Vega ... the dude behind south Florida's premiere customizing spot, The Auto Firm ... and he says the yuletide season has his spot JUMPING with baseball players looking to upgrade.

New York Yankees SS Starlin Castro brought his S50 AMG in and totally flipped it ... adding a full carbon fiber body kit, Avorza 22 inch Av37 forge wheels and all white custom leather interior.

Pablo Sandoval of the Boston Red Sox wasn't outdone by his Yankees rival ... adding a wide body kit, Avorza red and black leather and a custom exhaust system ... all setting him back $65k.

But the craziest job title went to Mariners RF Nelson Cruz... who dropped $40k on his Polaris slingshot ... adding a custom glow-in-the-dark paint job, a new sound system and 38 inch forged wheels.