Looking at how easy Povetkin was to hit the other night by a boxer with a bit of handspeed, i'd be shocked to see him go past 4 or 5 with AJ, even at this stage. Joshuas superior speed, strength, power and size would be way too much for Pov to deal with.
Joshua has all the potential but at this point in his career simply not enough experience to fight someone like Povetkin. Povetkin has like Joshua a great amateur pedigree but has in addition already fought the best of the best...
At this stage povetkin would win, Joshua wouldn't knock him out if wlad didn't. Give it a few years of development and AJ would handle povetkin.
Joshua too inexperienced as a pro to have a chance against a top seasoned heavy like Povetkin. Joshua may develop into a better fighter but now he only really has a punchers chance.
Joshua is far from ready at this stage. He was getting hit by that journeyman despite all the height/reach advantages. He is an elite talent and has great potential, possibly to rule the division in future, but Povetkin knocks him out.