McNeill agreed to a five-year contract extension through 2015 on Wednesday.
Wide receiver Legedu Naanee (hamstring) and linebacker (foot) are inactive for San Diego.
Rookie wide receiver Danario Alexander is active for St. Louis. Alexander was moved up from the practice squad this week after Mark Clayton was placed on season-ending injured reserve with a torn patella tendon in his right knee.
Backup linebacker David Vobora was active for St. Louis after being listed as questionable. Defensive tackle Clifton Ryan was inactive for the second consecutive week after being cleared following a bout with what the team called migraines.
Copyright 2010 by The Associated Press