The 5 biggest surprises from the first 5 days of March Madness

We knew March Madness would be filled with surprises, but not this many in the opening weekend of the 2021 NCAA Tournament.

One No. 1 seed has already gone home, while a 15th-seeded Cinderella from Tulsa has punched its ticket to the Sweet Sixteen.

Eight more games are set for Monday to determine the final teams destined for this weekend's regional semifinal round.

Before we witness more chaos in the closing matchups of the round of 32, let's recount the five biggest surprises from the first five days of March Madness.

No. 1 Illinois falls to familiar underdog

The second most popular pick to win the NCAA tournament fell early, when No. 1 Illinois dropped the ball against No. 8 Loyola-Chicago in the round of 32.

After cruising past 16th-seeded Drexel, 78-49 on Thursday, the Illini met their match in Loyola, who made a shocking run to the Final Four as a No. 11 seed in 2018.

Sister Jean's squad scored 14 points off 17 Illinois turnovers, and held the Big Ten tournament champs to 22.8% shooting from three.

The Ramblers never trailed in the 71-58 victory, and collected their 19th win in their last 20 games. 

Loyola will face No. 12 seed Oregon State in the Sweet Sixteen at 2:40 p.m. ET, Saturday, on CBS.

Pac-12 dominates opening-round action

Speaking of Oregon State, the Pac-12 conference has looked mighty dominant so far in the NCAA tournament, with all five of its representatives still unbeaten in the Big Dance, as of Sunday night.

In the final AP poll of the regular season, Colorado and USC were the only Pac-12 schools ranked in the top 25. The Trojans, as a No. 6 seed, trounced No. 11 Drake, 72-56, in the first round, and square off against Kansas on Monday night.

Patrick Ewing's 12th-seeded Georgetown squad was a popular pick to upset the No. 5 Colorado Buffaloes, but the runner-up of the Pac-12 tournament handled the Hoyas, 96-73, on Saturday. 

Pac-12 tournament champion Oregon State earned a No. 12 seed in the tournament and breezed past No. 5 Tennessee, before defeating No. 4 Oklahoma State.

Oregon will see its first game action against No. 2 Iowa on Monday afternoon, while the biggest surprise out of the Pac-12, UCLA, will face No. 14 Abilene Christian for a spot in the Sweet Sixteen.

The school with the most NCAA tournament titles entered March Madness as a First Four team and played Michigan State for a spot in the round of 64.

After defeating the Spartans, 86-80 in overtime, UCLA downed No. 6 BYU, 73-62, on Saturday night.

Only the Big Ten and Big 12 sent more teams (six each) into the second round.

COVID-19 complicates first round

No. 7 Oregon could come in cold against No. 2 Iowa on Monday, because the team has yet to play a game in the NCAA tournament.

In the round of 64, No. 10 VCU was scheduled to face the Ducks Saturday night, until several positive tests within the Rams program forced VCU to forfeit.

The matchup is the only no-contest of the tournament, thus far.

Georgia Tech was also impacted by COVID-19, as star forward Moses Wright was sidelined in the first round because of a positive test. Without Wright, the Yellow Jackets lost, 71-60 to Loyola.

The No. 8 seed Oklahoma Sooners also played without point guard De'Vion Harmon, who tested positive for COVID-19, but were able to edge past No. 9 Missouri Saturday.

Jason Preston shines for No. 13 seed Ohio

A Cinderella story in the making, junior guard Jason Preston helped lift No. 13 Ohio over defending tournament champion Virginia, who arrived late to the Indianapolis bubble because of their own COVID-19 issues.

In the 62-58 victory, Preston racked up 11 points, 13 rebounds, and eight assists in 40 minutes of play. In his postgame interview, he dedicated Ohio's victory to his late mother, who died when Preston was 16.

While in high school, Preston was hardly a blip on any college scout's radar, as he averaged 2.2 points and 1.2 assists per game. He almost quit the sport altogether, before heading off to college, but decided to spend a year in prep school, with the hopes of catching a college program's attention.

It wasn't until he posted a highlight tape on Twitter that Ohio came knocking.

Now as a junior, the Orlando native has emerged as a key playmaker for the Bobcats. During the regular season, he led the team in scoring (16.3 points), assists (7.3), and steals (1.5), and ranked second in rebounds (7.2).

Preston will write the latest chapter of his heartwarming saga when Ohio clashes with Creighton on Monday evening.

Double-digit seeds dance on

Nine double-digit seeds advanced to the second round of the NCAA tournament, which marked the second-highest total in history. Three of those are in the Sweet Sixteen, including Oregon State, No. 11 Syracuse, and No. 15 Oral Roberts. 

On Monday, at least one more double-digit seed will join the mix, once the outcome of No. 11 UCLA vs. No. 14 Abilene Christian is decided. No. 13 Ohio and No. 10 Maryland could also land a spot in the regional semifinal.

The record for the most double-digit seeds in the Sweet Sixteen is five, which occurred in 1999.

Oral Roberts is just the second No. 15 seed to make it to the Sweet Sixteen.

The 2021 NCAA tournament has also made history as the first to see four teams seeded No. 13 or higher advance to the round of 32.