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Seth Wenig/Associated Press

Every MLB team has a handful of X-factors on the roster.

For contenders, that player might be an up-and-coming prospect capable of filling a need, a young big leaguer still trying to realize his potential or a veteran being counted on to fill an important role.

For rebuilding clubs, it's more about the development of potential building blocks as the focus is on long-term outlook as opposed to immediate help.

We've taken a crack at naming the biggest X-factor for each MLB team during the upcoming season.

If these players can live up to their potential and deliver standout performances, their respective teams will be in considerably better spots as a result.