The Cards, wild card winners, will start their series with Washington at home. The Reds on the other hand, tied with Wash for the best record in the NL, both start on the road.
I still haven't actually figured out how or why Selig changed this. It's like picking the 2nd best kid in the group first to play on your team. Doesn't make any sense.
They play 162 games for a reason. The all star home field advantage in the WS was bad enough.