Barcelona are suffering in defence and that's a theme of this season. In the 19-20 campaign after 27 weeks they have let in 31 goals, keeping only eight clean sheets. That's an average of 1.15 goals let in per game. They have the sixth-best defence in the table. It has improved since Quique Setien took over though.
In the first 19 games, Valverde's side let in 23 goals and Ter Stegen managed five clean sheets, 1.21 per game. Setien has eight goals conceded in eight games, with three clean sheets.
By contrast, the previous worst campaign saw Barcelona concede 1.03 goals per game in 16-17. They let in 28 goals in 27 weeks but also kept 11 clean sheets. Real Madrid won the league that year.
In 15-16 the average was 0.81, with 11 cleans and 22 conceded between week 1 and 27. In 14-15, Barca let in 16 and kepy 15 clean sheets, 0.59 goals on average.
The best average was 0.48 in the 17-18 season. Barcelona let in 13 goals and kept 16 clean sheets. Impressive, although the season was seen as a failure after the painful collapse in Rome in the UCL.