The No.3-seeded Kirilenko was trailing the No.7-seeded Cornet in the first set, 5-0, when she was forced to stop play due to a left knee injury - afterwards she announced she is out of the tournament.
"I just want to say that I can't continue playing this tournament," Kirilenko told reporters in her press conference. "During the match I made a wrong step and felt pain in my knee - I feel so much pain right now that I can't continue here. Before the match it was fine - it happened during the match."
Cornet, a former World No.11, had beaten Kirilenko, a former World No.10, in all three of the pair's previous meetings as well - but the Frenchwoman maintained this one was far different from the others.
"From the first time I played her, I don't think she likes playing me that much, because I move well on the court and always make her play more and more shots," Cornet said. "But today I don't think it was the reason at all. She was injured, she was in pain, and she couldn't move normally on the court.
"I was playing great for five games, but she just couldn't play her best. I hope she recovers soon."
Could Cornet take any positives? "I got a little bit of luck today because she retired, and I knew it was going to be a very good match because she's a great player. I have two or more matches to play, so it's good to keep some energy for the next ones, even though of course it's too bad she was injured.
"I'll just take what I can from this one and give my best in the next one as well."
All three of Cornet's WTA titles have come on clay - Budapest in 2008, Bad Gastein in 2012, Strasbourg this year - so how does she rate her chances this week, where she's on indoor hardcourts?
"I think I'm definitely more of a clay court player, but I think with all of the years I've been playing and all of the work I've done with my coaches, I'm more and more of a hardcourt player now. I like playing on hardcourts more every year. My best wins this year have come on hardcourt - I've beaten two Top 20 players on hardcourt - and my game is starting to suit this surface much, much more these days.
"And here in Sofia it's a slower hardcourt, so I have more time to move and put more topspin on my forehand. So this hardcourt is especially good for me. I like it and hopefully I'll have a good week."
Kirilenko will be replaced in Group Serdika by Elina Svitolina, who was the first alternate here.