The Problem with Low Pocket Pairs
You limp in and see the flop: Ah Kc 8s. Now you're getting a little nervous since you see three overcards. Aces and Kings are popular to play, especially if they're together. While it's not likely somebody hit a two pair, it is likely somebody paired an Ace or a King, possibly an 8, and now has the best hand. If this is the case, there are now only 2 cards in the deck that can help you: a 7, and another 7. You're pretty much out of luck with your approximate 8% chance to win. If you didn't have a pocket pair, your odds of making a pair on the flop would be about 40%. Your odds of making a pair by showdown would be about 65%. This is much more in your favor than starting with a low pocket pair. The bottom line is that the odds are against you if you have a low pocket pair against two overcards since their chance of making a pair to beat you is about 65%, whereas your chance of making a set is only about 20%. Without getting into excruciating detail about odds and draws, you also need to keep suited connectors in mind when you have a pocket pair. If you have those same pocket 7's and you're up against two players, one holding 9T suited and one holding JQ suited, you're in a lot of trouble. Your two opponents will not only have that 65% chance of making a pair by showdown, but now you have to take into consideration their chances of making their straight or flush by showdown as well. Those pocket 7's are starting to sound like less and less of a playable hand now, aren't they?
*NOTE*: This article is describing the problem with pocket pairs vs. overcards. If you have pocket Aces or pocket Kings, the odds are much more in your favor, but bear in mind that even pocket Kings can fail with an Ace flop.