Heading into the 2011 MLB season, we all know about the players who are going to be their good old, productive selves. Roy Halladay is going to anchor a star-studed rotation, Albert Pujols is going to continue to hit bombs as a St. Louis Cardinal, at least for one more season, and Joey Votto will continue to show us why his 2010 National League MVP Award was no fluke—and those are just a few of the MLB’s consistent greats.

However, a baseball team is composed of 25 players, and they can’t all be All-Stars.

A lot of times, it’s a team’s role players that make them great. I think you needn’t look any further than the 2010 San Francisco Giants club, who won the World Series by riding the likes of rookie starting pitcher Madison Bumgarner and August waiver-claim, Cody Ross.

For the sake of this article, we’re going to call those types of players “wild cards.” Of course, I couldn’t go any further without establishing some sort of precedent. What exactly is a “wild card” player. In this article, a wild card player will be the type of guy that, in order of his respective team to have success, absolutely must have a good season.

Without this player, a hole is created on the team’s roster that, over the course of a 162 game season, will become a cause for concern. What are the criteria for being labeled a “wild card?” Basically, there are none. All players were eligible, and I only used a few, basic evaluators.

For example, players in similar situations were considered, but those with contenders were held to a higher regard. A majority of the players on this list are coming off of down or injured seasons, and teams that are relying heavily on said players are pushed further up the list.

So, without any further ado, here are the 15 biggest “wild cards” heading into the 2011 season.

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