He said one convicted murderer "couldn't accept that I was friends with black inmates".
Becker, 57, said the man wanted to kill him, leaving him in constant fear.
The German, who served his time in a British prison, added of losing his status while locked up: "In prison, you are a nobody.
"You are only a number. Mine was A2923EV.
Becker exploded on to the tennis scene in 1985 by winning Wimbledon at 17.
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