During the World Series of Poker, players are confronted with massive fields. In the 2007 WSOP, nearly 3,000 players bought into the first $1,500 No-Limit Hold 'em event. Throughout the Series, it was common to see starting fields of 1,500 to 2,000. Many poker players who are accustomed to playing in smaller poker tournaments can be overwhelmed by the prospect of competing against so many people. Some feel they need to make major adjustments to their games in order to be competitive. They play faster than they normally would, playing marginal hands and looking for opportunities to gamble.
I think this is a big mistake. You should never alter your strategy to compensate for the size of the field. When you sit down to play in a tournament, you should concentrate only on things you can control. Whether you're playing against 200 or 2,000 players, you should be focused on how you're going to beat the other players at your table. Let the rest of the tournament take care of itself. If you manage to make good decisions against your opponents, you'll have the opportunity to accumulate chips and survive as the field dwindles.
Think of it this way: if you were playing in a tournament where the blinds double every hour, the difference between beating a 300 person field and a 2,400 person field is a matter of surviving an extra three hours. If you manage to stick around, you'll have the opportunity for a nice payday. But if you gamble excessively in the early stages and bust out, you've got no chance at all.
In any poker tournament, the determining factor in whether you should play a given hand is the size of the blinds. If you have 10,000 in chips and the blinds are 50 and 100, there's no need to play A-J in early position. But if you have 10,000 in chips and the blinds are 1,000 and 2,000, you need to move in with that same hand. It's the blind structure that should determine how you play, not the number of players in the event.
In the WSOP Main Event, I've seen a lot of players feel pressured by the vast size of the field. But it's a false pressure. The Main Event has a great structure. The blinds increase slowly, so you can play patiently and look for your spots.
You can't win any large event in the first hour or the first day, so don't worry about what's happening elsewhere in a tournament. Play your game and do your best to beat the players at your table. It's the surest path to success in any tournament, no matter the size of the field.