There are a number of players who the Lions should retain (or try to, at least), but they didn't fit into the "high priority" category for one reason or another.
Let's address some of those here.
All Restricted or Exclusive-Rights Free Agents
The Lions have a bunch of talented players who are RFAs or ERFAs, and they will want to keep them. Guys like Joique Bell, Willie Young, Ricardo Silva, Amari Spievey and Jason Fox fall into this category.
But they don't count as a high priority, because the Lions don't have to prioritize them. They basically just sign them for a set amount, and that's it. It's more a procedure than a priority.
The Lions will absolutely make a bid to keep their top pass-rusher under contract, and understandably so. They have no natural DEs under contract, and Avril has been a big part of the defense.
But Avril doesn't get the "priority" tag because it seems increasingly likely that he'll be priced out of the Lions' range. The Lions won't use the franchise tag on him again this year. So it seems like everyone is somewhat resigned to letting him walk.
The Lions would love to keep Avril under contract, but they've clearly not been as adamant about it as they were last year.
Greg Jennings and Other Superstar-Caliber Players
OK, yes. It would be awesome to get Calvin Johnson and Greg Jennings in the same offense.
It would not, however, be awesome to put a quarter of the salary cap into the wide receiver position.
It was enough of a stretch to put Reggie Bush on this list, but I did it because Nate Burleson and Matthew Stafford are apparently lobbying for it, which would seem to indicate that the front office has at least some interest. It doesn't change the fact that the Lions have less than $2 million under the salary cap to spend, and the draft hasn't happened yet.
So while guys like Jennings, Jarius Byrd and Andy Levitre would probably be great players in Detroit, the salary cap is there for a reason, and it's going to prevent a lot of those moves from happening, especially this year.