NCAA tournament guide: Everything you need to know before filling out your brackets

March Madness is finally here.

A year after the NCAA men’s basketball tournament was canceled as the COVID-19 virus was mushrooming into a pandemic, all 68 teams will gather in Indiana for all 67 games beginning Thursday and ending April 5.

Here’s what you need to know before filling out your brackets this week:

When does the tournament start?

The “First Four’' play-in games begin Thursday. Instead of their usual home in Dayton, Ohio, the play-in games will be held in Indiana, where the entire tournament will be played this year to limit travel during the pandemic. Indianapolis, Bloomington (home of Indiana University) and West Lafayette (home of Purdue University) will be the major hubs. Here’s the “First Four”:

The first round — or Round of 64 — will be held Friday and Saturday, with the second round Sunday and Monday.

Here’s the full schedule:

Where can I watch the games?

CBS, TBS, TNT and truTV will broadcast the games on television. Games will also be streamed on the March Madness Live app.

Who are the top seeds?

Gonzaga earned the No. 1 overall seed after a dominant season, becoming the fifth team to enter the NCAA tournament undefeated since 1975-76. The West Coast Conference champion Bulldogs (26-0) — No. 1 in Ken Pomeroy’s efficiency rankings — lead the West Region.

Michigan, led by coach Juwan Howard, one of the members of the school’s famous “Fab Five” of the 1990s, sits atop the East Region. The Wolverines (20-4) earned their first No. 1 seed in the NCAA tournament since 1993.

Illinois, which won the Big Ten tournament Sunday after being denied the regular-season title, leads the Midwest Region. The Fighting Illini (23-6) tied a conference record with six wins over top-10 opponents this season.

Baylor, the top seed in the South, lost just one regular-season game before being eliminated by Oklahoma State in the Big 12 tournament semifinals. The Bears (22-2) rank third in the country in scoring at 84.4 points per game.

Which teams should be on upset alert?

No. 5 seed Villanova (16-6), which faces No. 12 seed Winthrop (23-1) on Friday, lost starting point guard Collin Gillespie to a knee injury last week and is riding a two-game losing streak after being eliminated by Providence in the Big East tournament. Gillespie, who shared conference Player of the Year honors with teammate Jeremiah Robinson-Earl, was averaging 14.0 points and 4.6 assists per game. The Eagles are no pushover, having cruised to the Big South title with just one loss.

No. 5 seed Colorado (22-8) faces No. 12 seed Georgetown (13-12), which might be the hottest team in the nation after its stunning run to the Big East tournament title. Coach Patrick Ewing’s squad is 10-4 since a midseason coronavirus shutdown, having outscored opponents by 14.3 points per game during its conference tournament run.

No. 5 seed Tennessee (18-8) is in a similar situation. Oregon State (17-12) made a surprise run to the Pac-12 tournament title to earn a No. 12 seed, upsetting UCLA, Oregon and Colorado. The Volunteers have lost three of their past six, including a 15-point setback to a disappointing Kentucky team.

No. 3 seed Arkansas (22-6) enters the tournament as one of the nation’s top-scoring teams, but will face a stiff test from No. 14 seed Colgate (14-1), which beat Loyola Maryland for the Patriot League title. The Raiders trail only top seed Gonzaga in scoring at 86.3 points per game and have a NET rating of ninth.

Also keep an eye on No. 3 seed Texas (vs. 14 seed Abilene Christian), No. 4 seed Purdue (vs. No. 13 seed North Texas), No. 4 seed Virginia (vs. No. 13 seed Ohio), No. 4 seed Oklahoma State (vs. No. 13 seed Liberty), No. 5 seed Creighton (vs. No. 12 seed UC Santa Barbara), No. 6 seed Texas Tech (vs. No. 11 seed Utah State) and No. 6 seed San Diego State (vs. No. 11 seed Syracuse), who are all just single-digit favorites heading into the first round.

What happens if a team has COVID problems?

Four teams that didn’t make it — Louisville (13-8), Colorado State (18-6), Saint Louis (14-6) and Mississippi (16-11) — have been put on standby. They could find their way into the bracket if a team in the field notifies the NCAA by Tuesday night that it must withdraw because of health concerns. After that, if a team pulls out, its opponent will advance via what is essentially a forfeit.

Players will get their own rooms and teams will have their own floors in a cluster of hotels around the Indianapolis downtown convention center. That facility, usually a magnet for fan fests and coaching conferences, will turn into the practice and meeting area for all the teams. Players will have to produce negative tests for seven days before arriving in Indianapolis to be eligible to play.

In one of its most eye-grabbing tidbits, the NCAA announced that if a team is hit with the virus but still has five players who can pass the protocol, that’s enough to get on the floor for tipoff.

The Associated Press contributed to this article.