Kirk's playing at the Freddie Mercury tribute

I've just put the Freddie Mercury Tribute show on, first time watching it in about 30 years, and I was a bit shocked at Kirk's playing. It's not as noticable in Sandman or Sad But True, but in Nothing Else Matters he sounds like a 13 year old who just picked up a basher accoustic for the first time.

A quick read online gave a few recounts that he was the one sober member of the band that day, but his playing is just not lining up with that.

Has anyone ever heard anything about why his playing was so bad that day?