he has room to improve in problem solving skill, espectially when it takes multiple steps and it need ability to connecting dots to get to the next level in his career.
I think assigning a mentor to him might be helpful. (这里看你自己想不想。想的话,自荐一下,你就成他领导了。再把自己手中的活推掉一些。因为你要花时间照顾他。)