These long, hard, hot stages can be unpredictable, there was no guarantee he would be better today and the final descent was not ideal to stay away either as showcased by Mas.
Some quick napkin math, he is 3:53 down, there are approx 6 MTF left and a few no-risk-no-glory type stages, final TT is twice as long as prologue and he got 35s on O'Connor there so could realistically gain a minute.
I think it's certainly doable but it's wide open and he'll have to fight it out 100% unless O'Connor cracks completely, not even counting some more riders doing these long range breakaway attacks and mixing it up.
Interesting times ahead, it won't be boring.