IIRC, Rams kept some cap space available in 2018 so they could make a "splash" signing in mid-season (Dante Fowler). Fowler gave a huge boost to the D after they picked him up in October. (Yes, it was via trade, but they needed the extra cap space to absorb his cap hit, as I recall).
Anyway-- I wouldn't be surprised if the Rams do something similar this year. They'll keep their powder dry for now, but then in late October (just before the trade deadline) Rams might splurge to add the last missing piece.