Jim Wyatt and Paul Kuharsky are at the Senior Bowl this week, and they are both reporting that Bob Bratkowski will be the Titans WR coach. Bratkowski is another one of Mike Mularkey's boys. He was the offensive coordinator in Jacksonville when Mularkey was the head coach there. Before coaching with Mularkey in Jacksonville, Bratkowski was the Cincinnati Bengals OC from 2001-2010. He has been back with the Bengals as an offensive assistant since 2014.
Bratkowski has one of the most important jobs on this staff. The Titans have invested a lot in receiver over the last few years with Kendall Wright, Justin Hunter and Dorial Green-Beckham.
For fun, do a Google image search of Bob Bratkowski.
Croom was also with the Jaguars in 2012. He has been with the Titans as RB coach since 2013. The Titans haven't been very good at running back in that time, but they also haven't had much talent at the position or a good offensive line. It is hard to say how good or bad of a job Croom has done.