Cal Ripken Jr. tells TMZ Sports ... there was only ONE pitcher he was TOO SCARED to face ... a pitcher who many consider the greatest of all time ... a pitcher who happens to be a woman.
Of course, the fireballer who put the fear of god into #8 is softball goddess Jennie Finch -- who struck out a bunch of MLB ballplayers in hitting challenges ... including Mike Piazza and Albert Pujols.
But Cal says he refused to face The Finch -- simply because he was just "too scared."
Can't really blame the guy.
Bonus: Cal also reveals his favorite baseball movie of all time ... and his explanation is pretty interesting.