The Patriots entered Saturday with only four wide receivers: Welker, Brandon Lloyd, Matthew Slater and Julian Edelman. Slater is primarily a special teamer, so this gives New England some depth if one of their top pass catchers goes down with an injury. Salas figures to battle Edelman for snaps behind Welker.
A highly productive player at Hawaii, Salas was a fourth-round draft pick last season. He was coming on strong in St. Louis in 2011 with 22 catches in his final four games before breaking his leg halfway through his rookie season.
With huge cash paid to tight ends Rob Gronkowski and Aaron Hernandez this offseason, Welker might leave New England in 2013 if he wants to max out his money. Salas will be one of the receivers in line potentially to replace him.
There were rumors that receiver Jabar Gaffney was hoping to re-sign with the Patriots when he gets healthy, but this move makes that less likely.
Follow Gregg Rosenthal on Twitter @greggrosenthal.