I can't see him getting KO'ed, he has a great chin. If anything the fight who is most likely to get KO'ed would be Lucus. Ultimately though I see Lucus outboxing Ruslan in a close 12 round decision.
Where's the evidence Ruslan has an iron chin, he wasn't KO'd by Corley, Bradley, Herrera and Algieri. That's a pretty featherfisted crew right there. Alvarado has some pop, but that much.
I don't see this guy getting KO'ed. Lucus will try and out box him and exploit Ruslan's inability to cut off the ring.
Here check these out for comparative power, Ruslan got shook a few times by Chop Chop but it goes the distance. http://www.youtube.com/watch?v=f2IhQehX_9c Whereas Matthysse stops him after dropping him 9 TIMES. http://www.youtube.com/watch?v=XjNWagsfVME