Originally Posted by Shakes

Lots of sports are played outdoors, where there is weather. Wind and rain are random, and can easily favour one side over the other.

Also, many sports decide who gets first use of the ball, or what end, by a coin flip. Again, a completely random factor that can impact the match. In athletics and swimming, lane draw plays a similar role.

Any game played on a non-artificial surface like grass will have randomness. Watch tennis on grass vs on a hard court: on grass the ball will sometimes skid through lower or higher than expected because of court wear. In cricket you see a ball hit a crack in the pitch and either take off or roll along the ground.

The balls are also all slightly different. In cricket they certainly wear at a different rate depending on a number of environmental and manufacturing factors. In something like baseball, I'm sure every ball is close but not identical in weight and dimensions, probably enough that it occasionally makes a difference between a home run and an outfield catch.

Along the equipment lines, you occasionally see a bat break or a racket string snap. That can certainly affect a match (point lost, scoring chance goes begging), and again, it's just random bad luck.

Then there's the refs, but that's a huge can of worms.

I think there's a heck of a lot more randomness in real life sports than a lot of people like to admit.