One of my uncles once said he likes baseball because it is so unpredictable. On any day the worst team can beat the best, the best hitters fail about 70% of the time, and the best teams rarely win more than 60% of their games.
This was exemplified today in one play in the Cubs-Phillies game. In the top of the 9th inning, the Phillies trailed 1-0 with a runner on second with two outs. On a ball hit to left field, the rookie right-fielder threw home as the runner tried to tie the game. The throw bounced to the catcher, who had just enough time to catch it and tag the runner. Except the catcher dropped the ball, the run scored, and the Phillies tacked on three more runs to win it. (Watch the replay here from MLB.com.)
This is one big reason to watch sports: it can be hard to predict how a single play might alter the course of the game.
And on a related note, not completing a play like this seems like one that happens to teams that are not very good. A better team would make the out to end the game. In baseball, it is very interesting how good teams always seem to get the breaks – most of which they probably make for themselves.