You've probably heard that the MLS Supplemental Draft takes place on Tuesday at 2 pm ET. And you probably can intuit that by the end of it, the 19 MLS clubs will have added a handful of potential players.

But you might be wondering what exactly the Supplemental Draft is. After all, it hasn't been held every year, and it's kind of unique in the North American sports world.

The best way to think about it is like this: The Supplemental Draft is the continuation of the SuperDraft.

The Supplemental Draft consists of four rounds, which are called Rounds 1 through 4, but in many ways it is Rounds 3 through 6 of the SuperDraft. (During last week's SuperDraft in Indianapolis, we overheard one club discussing trading their "third round" picks. What the club really meant was that they were looking to trade their first round picks in the Supplemental Draft.)

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The way it works

However, unlike the SuperDraft, which includes all the glitz and glamour that anything "super" deserves, the Supplemental Draft is done via a conference call with all 19 clubs and the league. That's not to say there aren't guidelines, though.

The Supplemental Draft guidelines are as follows:

Each club designates one person who is authorized to make draft selections.

Clubs are permitted three minutes to make a selection during each round of the draft.

There is a three-minute break between rounds.

If a club fails to make a selection in the allotted time, the next club in order will be permitted to make its selection. The club that failed to make its selection will then be given the opportunity to immediately make its selection. If no selection is made, it will have to again wait until the next club in order makes its selection.

Each club is given one three-minute timeout.

More than two timeouts may not be used consecutively.

Who's eligible?

The Supplemental Draft allows for only players who have finished their college eligibility and been nominated by an MLS club, as well as youth internationals made available by MLS.

Who's come out of the Supplemental Draft?

By its very nature, the Supplemental Draft is not where most of the blue-chip prospects are selected. But that's not to say there aren't more than a few Cinderella stories.

In fact, arguably MLS's greatest Cinderella story of all time started in the Supplemental Draft. San Jose's goal machine Chris Wondolowski, who won the MLS Golden Boot in 2010 and 2012, was taken in the fourth round of the 2005 Supplemental Draft.

Amazingly, he wasn't alone that year. Fellow fourth-rounders in 2005 include Chivas USA goalkeeper Dan Kennedy and Chicago Fire midfielder Jeff Larentowicz.

Other Supplemental Draft picks through the years include San Jose's Jason Hernandez (2005), New York's Kosuke Kimura (2007), New England's Chris Tierney (2008), and Philadelphia's Antoine Hoppenot (2012).

So who will emerge this year?