The Swedish defensive midfielder was in the right place at the right time, lashing the ball home in the last minute of added-time to help the hosts snatch a 1-1 first-leg draw.
"I'm not a real goal-scorer, it's not my specialty, therefore this goal is a special one for me," Wernbloom told reporters.
"My main job is to break the other team's attacks. I usually come forward only when we take a corner or a free-kick near the goal, so you could say I was a bit lucky tonight."
CSKA's frugal owner Yevgeny Giner bought Wernbloom from Dutch side AZ Alkmaar for a relatively modest three million euros last month.
"I think scoring a goal in such a game, he had justified his purchase," Giner said.
"Whatever we had paid for his transfer we already got it back with interest," he added with a smile.
The home side struggled to muster much of a threat with Ivory Coast striker Seydou Doumbia, who scored five goals in his five previous Champions League outings this season, being kept off the ball by the Spaniards' tight defence.
Wernbloom then came to the rescue to send a record 70,000-strong home crowd wild.
While Wernbloom tried to stay out of the spotlight, CSKA coach Leonid Slutsky singled out the 25-year-old for his overall performance.
"He's definitely one of our heroes," said Slutsky, who rarely praises individual players.
"Not only because he scored a very important goal for us but also his play was of high quality throughout the whole match."
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