Alright, since you asked - In the CL, we averaged roughly a goal a game given away regardless of his presence/absence. played 2 games with him - against Monaco and CSKA. We conceded 2 against Monaco and kept a clean sheet against CSKA. In the next three prior to his return as a late sub against CSKA, we conceded 3 goals (2 against Monaco and 1 against Leverkusen). We conceded one on his return in the final group game. So, not much impact there, even if we count/don't count the final game.
Next, a rough comparison of the seven PL games preceding his injury and the ones after his injury that he missed. We kept clean sheets against Palace, Stoke, Sunderland and City - we conceded one goal each against Everton, Liverpool and Middlesbrough. That's 3 goals in 7 games. Then came the West Brom game, where he got injured - not sure whether to count it or not, but we conceded one there. He missed the next six, finally returning for the game against United. In the next six games without him prior to United, we conceded 6 goals - 1 against Leicester, 1 against Arsenal, 2 against West Ham and 2 against Chelsea. He came back and we conceded again against United.
Ignoring the West Brom and United games (I'm not sure about how to count them - his injury and his return, effectively), we conceded 3 goals in 7 games with him and 6 goals in 6 without him.
That's an impact. A considerable one. One that Verts and Wanyama could not cover despite (as you pointed out) playing very well and stepping up to the challenge.
We missed him enormously.
As for selectively deciding which players are important, as I said, Toby, Hugo and possibly Dembele were Poch's heavy hitters last season. He missed one of them in the final two games, and folded - *if* Bale had been missing for AVB's final games, he might have folded, he might not. But Poch did fold - and did so with (arguably) two of his stars still left with him in Hugo and Toby. Thus, the one remains a possibility, the other remains a certainty - conversely, what remains a certainty is that AVB finished with more points than Poch did, having guided the team to a far more consistent finish than Poch managed. Now, the relative worth of his higher points tally versus Poch's higher 3rd place finish is the focus of this discussion - the side-track into Dembele versus Toby aside.
Not really. We'd already broken the 4th place hoodoo twice by that point, imo - in 2010 and 2012. But in 2011 and 2012, we'd faltered at the death (2011, we faltered pretty much throughout the second half of the season) and routinely failed to finish consistently. *That* was the hoodoo. I felt AVB broke it by finishing with 5 wins and 3 draws from his final eight, versus (as I mentioned) Poch's 3 wins, 3 draws and 2 defeats.
As for whether or not he could have gone one further and finished ahead of Arsenal if he'd beaten Fulham, perhaps, perhaps not. But if you're bringing that up, it's only fair to point out that
*not* abjectly, miserably being utterly destroyed 5-1 by an already relegated Saudi Sportswashing Machine side on the final day of the season would have allowed Poch to break that hoodoo (well, if we'd won, anyway). Sadly, he couldn't manage it either.