Man United manager Jose Mourinho says Marouane Fellaini was "lucky" to avoid serious injury following a challenge from Shane Long against Southampton.
Chelsea's disciplinary record is poor this season and the loss of composure has surprisingly come from some of the most experienced stars.
Once touted as the next big thing, William Carvalho's career has stagnated. However, a big performance against Barcelona would continue his revival.
Mathieu, 33, who spent three seasons at the Camp Nou, left for Sporting Lisbon on a free transfer.
The farcical situation between Edinson Cavani and Neymar is an unwanted sideshow as PSG look to beat Bayern to get their season on track.
As unlikely as it may sound, it seems Manchester United boss Jose Mourinho has become the latest member of Liverpool's most well-known fans' group.