Just curious. Other than attending college what other points of entry are there?
Almost as soon as the draft ends, teams start signing undrafted free agents…usually college players they liked but I guess an undrafted free agent could be pretty much anybody. I think the teams also sometimes have try-out camps open to the public. Think there’s a minimum age rule, too…something like three years after high school.
On occasion, teams will try players out from the various indoor and semi-pro teams across the country. Some even make it onto a game day roster, but it’s pretty rare. Most teams like developing their own talent, and there’s a large pool of undrafted free agents and castoffs from other teams.
Historically, the now defunct USFL was where players like Steve Young, Jim Kelly, and Herschel Walker got their starts. And NFL Europe was a decent development league, too.
Kelly was drafted by the Bills, but opted to join the USFL instead; the Bills retained his rights, and signed him after the USFL folded.
Young and Walker signed with the USFL before they would have been drafted by NFL teams; both were later drafted by the NFL (Young in a special supplemental draft).
I’d wager that most USFL players who wound up in the NFL would have been good enough to have been drafted by NFL teams anyway, if the USFL had never existed.
The CFL is another source which has seen a few of its players jump to the NFL over the years – Dolphins DE Cameron Wake is probably the most noteworthy example currently. He went undrafted out of college, was signed (and quickly cut) by the Giants after the draft, then parlayed two seasons of all-star play in the CFL into an NFL contract.
Warren Moon, Doug Flutie, and Jeff Garcia all played in the CFL before sticking in the NFL.
Kurt Warner went from Northern Iowa 1 year starting QB to
a tryout with the Packers (released before season) to
two years in the Arena Football League to
signing with the Rams and being sent to the European Football League and being 3rd string Ram QB for 1 year to
taking over for injured Trent Green to heading the Greatest Show on Turf.
Not quite what you were looking for, but…
Eric Swann was a first round draft pick in 1991. He didn’t attend college.
Michael Lewis is another player who never went to college. He went from driving a beer truck to signing for the Saints.
There have been a couple of Olympic track stars who have played (Renaldo Nehemiah and Bob Hayes). Several Aussie rules footballers have made the NFL as punters. One Swedish or Norwegian kicker made a YouTube video that went viral this year and was invited to try out (Detroit?)
There are also regional tryouts that anyone can go to for $275.
Tommy Maddox had a similar road, but with much different results.