Not sure how much an MRI is going to tell you about a back anyway. I remember when I was younger, I have a relative who is an MD and I told him my back was sore. He told me "everybody's back is sore at some time or another....get used to it."
The percentile of the whiff rate vs walk rate and the rate of suckiness / square root of Suzuki's birthday X3 says that all is well and the Cubs hitters are all fine. Hang in there.