I wouldn't say it was a lucky punch. It was just luck that it caught AJ right on the temple. AJ getting hit on the chin would have been better for him.
For those that want to hear the question and Ruiz's full answer, start the video at 5:51 instead of 6:30.
He was saying that in response to AJ claiming the left hand he (Ruiz) hurt him with first of all was lucky.
Right after Ruiz got up he ate a huge straight right hand and fired back eventually connecting with the left hook to Joshua's tender temple of which Joshua never recovered from... I won so much $$$ on the first fight I'm willing to lose $1,000 on the rematch and won't feel bad if I lose it, I'd still be way ahead! I'm not much of a gambler, it was a snap decision to do it the first time, didn't know what I was doing but it worked with a little Googling!!
When I won the first time I put $1,000 in the bank and used the rest to buy spot silver coins and silver has went up about $2 an ounce since I did so! That alone made me more than the $1,000 I'll lose if Ruiz comes in Fatter than Dustin Nichols just for the payday or there's some shady shenanigans going on that makes Ruiz lose!