As many assumed, the mystery player wearing No. 53 at Patriots practice today is indeed linebacker Marques Murrell.
Murrell wore 53 in his first go-round with the Patriots and when he was spotted at practice, he worked with the linebackers during positional work.
The Patriots do not have to make a corresponding roster move because they have a seven-day exemption for Brandon Spikes. Once that exemption runs out on Monday, a move will have to be made.