Asked by speed-academy.de to outline when he first realised his future with the struggling team for 2013 was in doubt, German Glock recalled the dying moments of last year's season finale in Brazil.
"We had really counted on being able to keep the tenth place," said the 30-year-old, who will be replaced with an as-yet undecided 'pay driver'.
In the meantime, Glock has already agreed a new deal to race for the front-running BMW team in Germany's DTM touring car championship.
Tenth place is lucrative in F1's constructors' world championship, because teams finishing lower miss out on crucial benefits as set out in the governing Concorde Agreement.
"That (Brazil) was when I began to concern myself with the subject," said Glock, recalling the moment when he realised his F1 future might be in doubt.
"The team came to me and told me very clearly and openly what is the situation. I made my thoughts about it and eventually we sat down together and went through the certain possibilities," he revealed.
"I then realised how difficult was the economic situation for the team, and that it would therefore be difficult to make the expected step forward.
"We now have a good base and I also believe that the new car will be a step forward," continued Glock. "But, still, I know what it takes to make the really big step," said the former Toyota driver.