Dockett sustained a right knee injury during Monday's practice, spurring an MRI, Darren Urban of the Cardinals' official site reports. Dockett required the use of a cart to leave the field, but the severity of the ailment likely won't be known until the aforementioned MRI is performed. If he misses any time, rookie Kareem Martin and holdover Frostee Rucker will further factor into the mix at defensive end.