Sparked by Josh Allen, who has accounted for 33 TD's, the Bills have a top-10 offense. Now the Bills' defense is coming around to where it was during the previous three seasons when it was one of the league's best. Buffalo's pass defense has a 7-to-8 touchdown-to-interception ratio in its last six games after giving up 12 TD throws with just two interceptions during the first six games. 
As the Bills become a more complete team, the Steelers are regressing. This isn't surprising since Pittsburgh had won six games by an average of 4.8 points. 
The Steelers' ground game has gone from mediocre to one of the worst in the league and their defense has been hit hard by multiple linebacker injuries. Losing Devin Bush and Bud Dupree really hurts their pass coverage. 
Both teams played on Monday, but the Steelers have to make the journey to upstate New York and will be playing for the third time in 11 days. 
The Bills defeated the Steelers, 17-10, at Pittsburgh last season and Buffalo is better this season.