Eduardo was subjected to a brutal challenge by Birmingham City's Martin Taylor last weekend, resulting in a horrific leg break and ankle dislocation.
The 25-year is set to face no less than nine months on the sidelines, but was fortunate not to see his career ended.
"The injury was so grave I could have lost my foot," he told the News of the World.
"So I will always be grateful to Gary for what he did in lowering the risk to my leg. That was decisive. I do not remember too much about the blow.
"I remember the pain, seeing that my foot had rotated, but I only recaptured my senses in hospital."
Lewin immediately recalled Arsenal substitute Gilberto Silva from the bench to act as an interpreter between him and the Brazilian-born Eduardo.
Terry Incident
Lewin, who is England's physio as well, was also credited for saving John Terry's life during the Gunners' 2-1 defeat by Chelsea in last year's Carling Cup final.
The Arsenal physio rushed onto the Cardiff pitch as soon as Terry fell unconscious, and dislodged his tongue after he was caught by Abou Diaby's boot.
The Chelsea skipper headed to Arsenal's dressing room after the game to thank Lewin for his action.