Justin Bieber has Bieber Fever -- Shane Bieber Fever, that is.
The most unlikely long-distance friendship is blossoming between the "I Don't Care" singer and the Cleveland Indians ace ... with the Biebs getting his own "Not Shane Bieber" Tribe jersey!!!
Of course ... Shane has worn "Not Justin" on his back for the past 2 MLB Players' Weekends, when the athletes get to wear whatever name they want on their jerseys.
JB is getting in on the fun now ... rockin' his very own Tribe jersey while joy ridin' on his motorcycle in Beverly Hills on Tuesday.