Alonso lost a fresh engine in Italy which upset the whole plan in terms of PU allocation. Ferrari then didn't want to use a sixth one, so he hardly let Alonso did any lap in practacies in Austin, Brazil and had to pary for the PU to pull through.
Alonso had another failure today which led to missing the most important practice session. He has just told he won't be able to do many laps tomorrow, because they have to save the engine. This means two handicaps: firstly he will arrive in qualy with only a few laps in his bag, secondly another defensive approach in the race.
Why didn't Ferrari put a new PU in Austin where overtaking isn't that hard. And anyway: Alonso has no chance for the title or for a win or even for a 3rd place in the championship. They would have let him enjoy his last races in scarlet.