Routis was given a straight red card after fourteen minutes for bringing down Preston's Joe Garner as the striker looked to race clear into City's penalty with only goalkeeper Ben Williams to beat.
If, as expected, match referee Mark Heywood puts the dismissal down as 'denying a goal or clear goalscoring opportunity' then Routis will have to serve out a one-match ban. This would mean the Frenchman missing out on this Saturday's Sky Bet League 1 fixture against the Gills.
With Andrew Davies and Gary MacKenzie out injured for the Preston match, Gary Liddle had to fill in for Routis at centre half before City switched to a back three during the second period.