They absolutely had the money to sign him and decided not to. Heres just a few of the offseason moves
S Marcus Williams (tendered at $10.612M; re-signed) - Left the following year to join the Ravens anyways
DE Tanoh Kpassagnon (UFA Chiefs; $4.5M/2 yrs, $2M gtd/$500K SB) - Hasn't really worked out so far
TE Nick Vannett (FA Broncos; $8M/3 yrs, $3.8M gtd/$900K SB) - Did anyone even know he was on the roster?
Just for clarity, Hendrickson's contract was 4 years with only 16 million guaranteed.
The simple truth is, DA didn't recognize his talent and know how to use it much like Baun. This was a common theme in the front 7 under DA. All he did was aquire and coach up secondary talent. His defense survived off of coverage pressure and sacks. Once we lost Onyemata (another really good front 7), our run defense went to trash.
It certainly looks reasonable to make the assumption that DA was so arrogant about his secondary he believed front 7 talent wasn't very important since he had Jordan and Davis anchoring it. Either that, or he just simply had no idea what front 7 talent looks like and simply kept Davis and Jordan because their known names. Pick your poison. Theres not really any wiggle room for anything else.