Simpson said he first noticed a problem the night before the game. He was unable to specify either the location of the injury or the problems it caused him, but he was clear that it limited him from playing to his full ability.
"I just felt like my foot was kind of asleep, I guess," Simpson said. "Until we know the diagnostics, I really can't (say) if it's a foot, a calf or what. I really don't know right now."
Simpson, who the Minnesota Vikings acquired via free agency this past offseason, was suspended for the first three games of the 2012 season for violating the league's substance abuse policy. Simpson caught four passes for 50 yards in Minnesota's Week 4 victory over the Detroit Lions, but he did not catch a ball in his limited playing time Sunday.
Simpson had 725 receiving yards and four touchdowns with the Cincinnati Bengals last season.