http://www.fangraphs.com/blogs/matt-shoemaker-borrows-from-the-tanaka-playbook/
"Shoemaker’s splitter isn’t elite; unlike with Tanaka"
Hopefully this change that Shoemaker's made allows him to have continued success, and although he isn't at Tanaka's level, getting decent starts from him definitely will aid the Angels this year.
In regards to injury concerns, Tanaka had the partial tear of the UCL that he healed without TJs, so there's of course that to be worried about if Shoemaker continues down this path.