Jackson was injured during the second quarter. On his Twitter feed, Jackson said the groin was making progress, and he also reported he had undergone acupuncture treatment.
"Steven's a warrior, and you almost have to pull him back," Spagnuolo said. "What you don't want to do is get him out there too soon and set him back. We're all happy it wasn't anything worse, and now it's just a matter of treatments and making sure we don't make it any worse."
Washington is known as a hard-hitting special-teams player and a tough runner. He was a seventh-round pick by the Jacksonville Jaguars in 2008, and he appeared in six games as a rookie, primarily on special teams.
The Associated Press contributed to this report.