HENDERSON, Nev. -- Las Vegas Raiders safety Lonnie Johnson Jr. suffered a broken fibula during Saturday's practice at Allegiant Stadium, a source told ESPN's Jeremy Fowler.
Johnson will get an MRI to determine if there is additional damage.
The six-year veteran was carted off the field after he collided with defensive end Maxx Crosby while attempting to tackle running back Raheem Mostert.
Johnson, a projected backup, has been competing for a rotational role in the Raiders' secondary. During training camp, he has received first-team reps whenever the defense has three safeties on the field.