Players with talent that don’t get drafted get signed as UDFA’s (Undrafted Free Agents) and each team signs about a dozen or so UDFA’s right after the draft with the hopes of finding a diamond in the rough, so if any NFL teams felt there were more talented players than Sam, they could easily sign them as an UDFA so it’s not like Sam took away anyone’s chance to play.
If a team had a player on their board but didn’t draft him, then they offer him a UDFA contract.
Just because someone isn’t drafted doesn’t mean they are not allowed to play in the NFL.
Kurt Warner was never drafted, yet he was a two-time league MVP as well as a Super Bowl MVP and took two of the leagues worst franchises to the Super Bowl, winning SB 34 in 2000 when a year before, no one outside of the Rams and their fans had ever heard of him.
As for Sam, he will have little chance to make the Rams squad. He would have likely had a better chance to catch on with a 3-4 team who needed depth.