I guess Sevilla focused on this game and they know Manchester United is a strong team, however in Manchester United, there is a possibility for them to have some injured players against Sevilla which can make this team unpredictable, but I guess Sevilla should be full defensive and don't let Manchester United use space for their midfielders and take control.
These two teams have met in the Europa League in 19/20, and the result was 2-1 Sevilla. From several other matches, Manchester United have never won with Sevilla. We cannot assume Sevilla is a weak opponent for Manchester United. The performance of Manchester United players has been relatively good lately this season. But Sevilla will play more aggressively, not to defend.