Perhaps you played college basketball or just fancy yourself an expert bracketologist because you won your pool back when Kentucky actually made the national tournament. Maybe youve spent this March obsessing over one-bid conferences you wont remember until next March. Losing $20 might be as much a personal rite around this time of year as allergies in Atlanta or the green-dyed Chicago River.

No matter your status, know this before you make your forecast for the N.C.A.A.s Division I men's basketball tournament: The bracket that will be released on Sunday evening will not have been designed quite like its predecessors. Blame the coronavirus pandemic.

In a typical year, the selection committee considers a teams proximity to the scattered sites that host preliminary rounds. But with all 67 of this years games planned for Indiana because of the pandemic, geography simply does not matter as much.

So meet, for 2021, the field-wide S-curve.

This system, while new to the mens tournament, has been used for years in the womens competition to design its tournament field, which will be announced on Monday, with games starting in Texas on March 21.

The start of the process is familiar: The selection committee will place the top four overall seeds into four separate regions.

Then the so-called snaking begins. The fifth overall seed plays in the same region as the No. 4. The No. 6 team will share a region with No. 3. Tabbed as the seventh seed? You may wind up dealing with the tournaments No. 2 team. The eighth seed will be placed in the No. 1 seeds region.

And on and on it goes until the tournaments top 64 teams have their opening positions. (For those of you who play fantasy sports, it will look a lot like your yearly draft.)

Of course, things may not actually be that simple because this is college basketball, and there are all sorts of caveats and catches. Among the considerations the selection committee will weigh:

The mens play-in games on Thursday will, as usual, feature four games between the last teams seeded in the bracket, including some low-ranked conference winners and the final at-large bids.

The field is expected to include 37 at-large teams, as well as 31 teams that earned what are known as automatic qualifier bids in their leagues. The leagues that receive automatic bids for at least one team range from the powerful conferences, like the Big Ten and the Southeastern, to the ones that often draw less notice, like the Big South and the Ohio Valley.

The Ivy League ordinarily has a bid, but its teams did not play basketball this season.