Plenty of players from days gone by could be introduced to a modern audience, for reasons other than nostalgia.

With the NFL revolutionizing the numbering system for players, there’s an unintended consequence that could play out for several teams. With a wide swath of players now able to wear single-digit numbers and other significant changes expanding the numbers that players can wear, the chances of players wanting to wear numbers that currently are retired will increase.

It happened earlier this year, when J.J. Watt joined the Cardinals and the family of Marshall Goldberg agreed to let Watt wear No. 99 — and when the Cardinals didn’t say to all involved, “Sorry, but retired means retired.”

As single-digit numbers go, the following are off limits, until of course they aren’t: Cardinals 8 (Larry Wilson); Bears 3 (Bronko Nagurski), 5 (George McAfee), 7 (George Halas); Broncos 7 (John Elway); Lions 7 (Dutch Clark); Packers 3 (Tony Canadeo), 4 (Brett Favre); Chiefs 3 (Jan Stenerud); Rams 7 (Bob Waterfield); Giants 1 (Ray Flaherty), 4 (Tuffy Leemans), 7 (Mel Hein); Eagles 5 (Donovan McNabb); 49ers 8 (Steve Young); Oilers/Titans 1 (Warren Moon), 9 (Steve McNair).

Given that linebackers can now wear numbers from 1 through 49 and running backs can wear numbers in the 80s, other issues could arise. For each team that confronts a question like this, the answer ultimately will hinge on whether retired actually means retired.