(Note that the concept of a first pick of the draft is not interchangeable with a first round pick. Jim Kelly, for example, was a first round pick. But he wasn't the Bills' first pick of the draft, because the Bills chose a TE two picks earlier.)
During the post-Polian/pre-Nix era, the Bills have used first picks of the draft on the following DBs:
- Thomas Smith. Result: seven years of decent play
- Jeff Burris. Result: left the team after four years. Had a ten year career.
- Antoine Winfield. Result: left the team after five years. Had a thirteen year career.
- Nate Clements. Result: left the team after six years. Has had an eleven year career thus far.
- Donte Whitner. Result: bust
- Leodis McKelvin. Result: bust
There are no success stories on the above list. Some of the DBs left early because they were busts, and some left early because the team decided to let them go first-contract-and-out. Either way, first round DBs didn't stay long. The Bills responded by using early picks on the replacements for those DBs.
In the post-Polian/pre-Nix era, the Bills have used first picks of the draft on the following RBs:
- Antowain Smith. Result: bust
- Willis McGahee. Result: disappointment
- Marshawn Lynch. Result: bust
The above list would be longer if it included Travis Henry (second round) and Spiller (a Nix pick). Also, Butler only used one first or second round pick on a RB, which means he used early picks on RBs at a much lower rate than TD or Marv. (Which is one of the things Butler did right.) Needless to say, there are no success stories on the above list.
I'm not suggesting that it's always a mistake for a team to use a first round pick on a RB or DB. If Antoine Winfield, for example, had been retained for the entirety of his career, he would have represented an excellent use of the Bills' first round pick. The reason Antoine Winfield didn't become a success story for the Bills was because of their strategy of allowing their best DBs to go first-contract-and-out.
During the post-Polian era, the Bills have had severe problems at QB and on the offensive line. They used three first round picks on the QB position: Rob Johnson, Drew Bledsoe, and JP Losman. One of those was a trade for another team's aging backup, and did not represent a real effort to find a long-term solution to the problem at QB. That means just two first round picks were used on attempts to find a long-term answer at quarterback, as opposed to nine on DBs + RBs. Similarly, only two first round picks were used on OTs during the post-Polian era, despite the fact the Bills' offensive line has typically been disappointing at best during that time.
Bill from NYC's opposition to using early picks on RBs or DBs is a rational response to the last 20 years of Bills' history. The number of early picks used on those positions has been excessive, and not once during the post-Polian/pre-Nix era has any first round DB or RB resulted in a success story. The team has had very severe problems elsewhere--especially at QB and on the OL--because too many picks were squandered on RBs and DBs.
But just because Nix has used first round picks on a RB and a DB, does not necessarily mean he's falling into the same trap as his predecessors. One of the reasons the post-Polian first round RBs were busts was because none of them were anything special at catching passes out of the backfield. Spiller might be. He also seems like a faster, more elusive runner than the other post-Polian first round RBs.
The problem with post-Polian DBs has been that even when a first round pick was successful (a good player) it was still a failure (first-contract-and-out). Thus far, Nix has been very good at keeping the players worth keeping. This means that if Gilmore plays well, there's a chance he'll be retained for most or all his career.
If Spiller and Gilmore turn into success stories, they will do two things. 1) Strengthen the team at RB and DB, respectively. 2) Discourage the team from using first round picks on RBs and DBs, thereby freeing those picks up for use elsewhere.