Unlike Matthews, who didn't practice at all Monday because of knee soreness, Lacy's problem actually occurred during practice. He dropped out late in the session and did not return with what coach Mike McCarthy said afterward was a sore foot.
James Starks finished the practice in Lacy's place with the No. 1 offense.
"Eddie had some foot soreness," McCarthy said. "They just pulled him out there near the end."
The Packers were careful this offseason not to overwork Lacy in practice, but when training camp opened last week, Lacy took his usual workload.
The Packers could be thin at running back if Lacy is out for any extended period of time. Rookie John Crockett (ankle) remains on the physically unable to perform list, leaving Starks, Rajion Neal and Alonzo Harris as the only other available backs.
McCarthy said he had no update on Matthews, who also did not practice Tuesday. Matthews spent the early portion of practice inside the Don Hutson Center in rehabilitation before coming out to watch the second half.
The Packers do not practice Wednesday. They have meetings but will not be on the field again until Thursday morning.