The Belgium international recieved treatment at Chelea's Cobham Training Centre on Friday as the rest of the squad either took part in a full training session or a recovery session, depending on their workload against BATE. Ethan Ampadu (knee) is the only other injury issue for the Blues.
Chelsea still managed to defeat BATE on the strength of a hat-trick from Ruben Loftus-Cheek, and could be forced to aim for their second straight win without Hazard's services.
Chelsea boss Maurizio Sarri admitted prior to the match against BATE that Hazard's status for Sunday's game at Turf Moor was up in the air.
"[Thursday], he is out for sure. He has a back problem," Sarri said. "We are trying to solve the problem for Sunday, it is not very easy."
Hazard suffered the back injury in Saturday's 2-2 draw with Manchester United, playing the full match but grimacing in pain at times while holding his back.
The 27-year-old has been in stunning form for the Blues this season, netting eight goals in 11 appearances in all competition to lead the team in scoring.
Hazard has not yet been ruled out of Saturday's training session, the club's final preparation before Sunday's trip to east Lancashire.
The Blues are undefeated in the Premier League thus far, winning six and drawing three to sit two points behind co-leaders Liverpool and Man City.