One thing I noticed during the fight Chagaev landed (what appeared to be from memory) a decent sized left over the top after a clinch that landed right on Wlad's chin.. It's hard to tell how he'd have reacted if he had to fight on because it was just at the bell but Wlad seemed to take it just fine.. contrary to conventional wisdom.
[YT]http://www.youtube.com/watch?v=794vgjOwZqI[/YT] Wasn't paying attention but I did see Wlad step on Ruslan's foot which looks like it affected his balance on the kd in the 2nd. Around 2:02
The 2nd round knockdown happened because Chaggy was off-balance. IMO Chaggy has an excellent chin. On another note he was totally outboxxed and IMO I thought Chaggy would have done better. Wvlad is a very good boxer.