The Lions are now down to 75 players. After releasing Tyler Polumbus this morning, the final move to get down to 75 was moving cornerback Jack Williams to the reserve physically unable to perform list.
Williams missed all of training camp and was on the active PUP list. That meant that he couldn't practice and counted for a spot on the Lions' roster, but he could have been activated at any time.
Now that Williams is on the reserve PUP list, he will not be eligible to play for the first six weeks of the regular season. It also means that he no longer counts for a spot on the roster, which is how the Lions got down to 75 players.