When in the Thrilla in Manila do you think Ali realised start to realise what he was in for?

I think in the 6th round Ali realised that this was going to be a much harder fight than he expected.

He was still clowning in the 5th and got caught with a good left hook but it was in the 6th where he got nailed twice to the head in quick succession.

But I think it was in the 8th round where he realised that this was going to be hell because he battered Frazier at the start of the round but Frazier came back and in my opinion ended up winning the round.

That must have been so discouraging for Ali.