I'd also point out to the OP that most accidents where crew fatigue is a factor - though not the only factor - occur at landing. The CO Q400 crash near BUF last year had a definite crew fatigue contribution. Landing, especially at an airport like YYZ, means having your full wits about you because there are all kinds of lineup, separation, descent altitudes, vectors and speeds, runway traffic, issues to take into consideration with many, many flights in the ATC environment. It can be plenty disorienting if you are half asleep.

If the pilot of the OP's flight was fatigued coming into LAS, he would have been that much more fatigued four hours hence. Here's little reading on pilot fatigue. There's lots of it on the internet.

http://www.cbc.ca/canada/story/2010/...atigue025.html