Pedro de la Rosa knew before travelling to Canada that there was a chance he could be racing the Sauber this weekend.
The veteran Spaniard admitted earlier that he found out for sure just minutes before second practice, when regular Sergio Perez reported unwell.
But the news that Sauber tentatively arranged his loan from McLaren some days ago is a further blow to the team's official Mexican reserve Esteban Gutierrez, who is reportedly unhappy about missing out on the drive and is not even in Canada.
"It was before I went to Canada," de la Rosa told Mundo Deportivo newspaper when asked when the prospect of replacing Perez was first raised.
"Martin Whitmarsh told me that Sauber had contacted him to see if it would be possible to replace Sergio if necessary.
"But I didn't really think about it and forgot about it when I saw Perez doing the first session," he explained.
The report said Sauber did not want rookie Gutierrez, 19, learning the hopes in formula one on the treacherous Circuit Gilles Villeneuve.
De la Rosa, 40, told Sonntagsblick newspaper that even he struggled at the wheel of the unfamiliar C30, despite racing its predecessor a year ago.
There was just not enough time to learn the steering wheel
"I constantly pressed the wrong buttons. There was just not enough time to learn the steering wheel," he said.
Spanish sports newspaper Marca reports that his unfamiliarity was a factor in his crash before qualifying, after pressing the 'DRS' button instead of deploying KERS.
And in a message to Perez, de la Rosa said: "I'm sorry you were unwell but I'm sure you'll come back stronger. My long career is ending and yours is just beginning."