A baseball player under the leaning tower

I am a licensed tourist guide in Tuscany and some time I have the opportunity to Know interesting people. Some of them are or were famous people.
The companion of this tourist group told me that the man on the left side in the picture, was a famous baseball player. Even if I was a little italian player of baseball in Lucca, I really don't know who he was.
Is any body able to Know him?
This is like a message in the bottle for the american baseball supporters with a good memory.
G.