In a statement released on Monday night, the NCAA said one of the officials had tested positive for COVID-19 and was sent home from the tournament’s controlled environment, along with five other officials who had interacted with him.

Four new referees from a pool of reserves have been appointed in place of the officials who were withdrawn from the men’s basketball tournament, while two will not be replaced.

The NCAA has selected a total of 60 referees for this year’s tournament, which gets underway on March 18 with the First Four games.

“The NCAA has replaced several officials for March Madness because of a positive COVID-19 test,” the NCAA statement read.

“One official tested positive March 15, and five other officials the person interacted with the day before were identified as exposure risks due to prolonged close contact.

“Based on tournament protocols and contract tracing with local public health authorities, these officials may not participate in the tournament. The infected official must be placed in isolation, and the other officials must be placed in quarantine.”

According to Stadium, the referees sent home included Ted Valentine, John Higgins and Roger Ayers.

Twelve months ago the men’s basketball tournament was canceled for the first time since its inception in 1939 because of the coronavirus pandemic. As the outbreak ground sports to a halt across the U.S. and the world, the NCAA was forced to cancel all its championship events for the remainder of the academic season.

A year on, March Madness is set to make its return, albeit with a slightly different look. Due to the logistical challenge posed by keeping 68 teams in a controlled environment, the NCAA announced in January that the entirety of the tournament will take place in Indiana.

Six different sites across central Indiana and the Indianapolis metropolitan area will be used, including the arenas of Purdue University, Indiana University Bloomington, Ball State University, Butler University and Indiana University-Purdue University Indianapolis.

Lucas Oil Stadium, the home of NFL franchise Indianapolis Colts, will host games in the first two rounds, as well as the Elite Eight and Final Four.

The venue was originally scheduled to host only the Final Four, with the previous rounds set to be held on a regional basis, until the COVID-19 outbreak forced the NCAA to redraw its plans.

Much as it’s been the case for its professional counterparts, coronavirus has been an ongoing issue for the NCAA. Last week, Kansas and Virginia withdrew from the Big 12 and ACC tournaments respectively and it remains unclear which players will be available for both schools later this week.

A team typically has 12 players for a game roster, but the NCAA said five healthy, eligible players will be enough for a game roster for this unprecedented tournament format.

“We decided if they had five players eligible and healthy, if the team was good to go,” NCAA senior VP of basketball Dan Gavitt said last week. “We wrestled with contingencies, and thought it was fairest for a team that earned its way, that even if it was compromised, they should have the opportunity to play rather than be replaced.”

The NCAA has put four teams on standby—Colorado State, Louisville, Saint Louis and Mississippi—as replacements, should one of the 68 teams that have been selected for March Madness have to withdraw. As per NCAA, teams have until Tuesday to notify the organizers if they can’t meet the protocols in place in the Indianapolis bubble.

Programs that are forced to pull out by Tuesday will be replaced by one of the four replacement teams, but if the withdrawal comes after the Tuesday deadline teams will not be replaced and their opponents will advance instead.

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