The attacking midfielder, who is on loan at Los Che from Real Madrid, has picked up yet another serious knee knock, and could be out of action for six months
The 21-year-old featured from the start in the second leg of the semi-final tie, but was stretchered off the pitch around the hour mark after twisting his knee.
Canales underwent further examination on Friday, and Valencia have now confirmed that the attacking midfielder has damaged ligaments, and will consequently be unavailable for about six months.
Canales had only just returned to full match fitness after spending several months on the sidelines due to another knee problem.
The Spain Under-21 starlet joined Valencia from Real Madrid on a two-year loan deal at the start of the season, but his ongoing injury problems have prevented him from making an impact at Los Che so far.
Starting last month and continuing for 10 weeks, Goal.com is publishing exclusive extracts from Luca Caioli's new book, Ronaldo: The Obsession for Perfection. The sixth extract, published on Friday, looks at his display for Man Utd in the 2008 Champions League final against Chelsea in Moscow, including the Portuguese's missed penalty in the shoot-out. Don't miss it!