It's unclear when Swift suffered the concussion. The rookie tailback wasn't listed on the Lions' official injury report Wednesday, and he spoke with media members following practice that day.
If Swift is unable to clear the league's concussion protocol before Sunday's game, veteran running back Adrian Peterson would likely regain the starting job. Kerryon Johnson also would likely see an increase in playing time.
Swift is coming off the first start of his NFL career last week against the Washington Football Team. In that game, he rushed for 81 yards on 16 carries and caught five passes for 68 yards and a touchdown.
In nine games this season, Swift has 331 rushing yards and four touchdowns on 70 carries. He also has recorded 31 receptions for 275 yards and two receiving scores.
Meanwhile, quarterback Matthew Stafford practiced on a limited basis Thursday as he continues to deal with a right thumb injury. Lions receiver Marvin Jones Jr. (knee) and tight end T.J. Hockenson (toe) also got in limited practices.
Kenny Golladay sat out practice Thursday after he returned to practice Wednesday for the first time since sustaining a hip injury against the Indianapolis Colts. Fellow wideout Danny Amendola also missed his second consecutive practice because of a hip ailment.