Ok so I went to check the number of De Vrij and Acerbi
De Vrij was on the pitch in 6 CL games and we conceded 7 goals in that time. 1 clean sheets when he played + 1 half time clean sheet.
Acerbi was on the pitch in 6 CL games and we conceded 4 goals in that time. 3 clean sheets when he played + a 15 minutes cameo without conceding.
De Vrij was on the pitch in 25 games in Serie A (starting eleven 17 games, subbed in in 8 games).
When he played from the start we conceded 5 goals, 11 clean sheets when full minutes. Those minutes he was coming off the bench, we didn't concede a goal in Serie A.
The games we did concede when he was playing full minutes were a 1:2 win against Atalanta, a draw against Juventus, a 1:5 win against Monza, a 2:1 win against Genoa and a 1:0 loss to Sassuolo.
Acerbi was on the pitch in 27 games in Serie A (starting eleven 24 games, subbed in 3 games).
When he played from the start we conceded 16 goals, 12 clean sheets when full minutes. Those minutes he was coming off the bench, we didn't concede a goal in Serie A.
The games we did concede when he was playing full minutes were the 5:1 win against AC Milan, 1:2 loss against Sassuolo, 2:2 draw against Bologna, 1:2 win against Atalanta, 1:1 against Juventus, 1:1 against Genoa, 2:1 win against Hellas Verona, 1:1 against Napoli, 1:2 win against Udinese, 2:2 against Cagliari, 1:2 win against AC Milan. Acerbi also featured for 63' minutes in a win against Roma, where we conceded 2 goals while he was on the pitch.
So what it seems is that Acerbi had a worse Serie A campaign, but he did better than De Vrij in CL. If Acerbi is rested, he is a beast, while De Vrij seems to be a creature of habit. If he has a run of games, he'll deliver against most teams - which is why I want him to stay for at least 2 more seasons.
When De Vrij started, we only lost 5 points in Serie A.