I am a big Ivan fan and hope he can tweak some things enough to keep progressing. Making the transition and moving up to the big leagues is extremely difficult, even for very good college players. His hitting, especially power, has carried him, but he had too many Ks in college and does not seem to have improved that too much in the pros. To get to the bigs he probably needs to improve on at least one of those. As Blake mentioned, it probably won't be his D that helps him.
I worry about our current players for the same reasons. If you can't hit a curve and always chase them you are doomed. A little bit of power and a bad batting average won't get you far unless you are excellent in the field- and that partially depends on the position. Even if you can hit for a reasonable or good average, without some power or an excellent glove and arm for the right position or really good speed it still can be hard to make it.