Three days before a must-win game, the Giants lost their most irreplaceable player, their offensive coordinator and a practice evaluation of their injured starting quarterback.

The cumulative sum is their biggest disruption in this coronavirus-rattled season.

Top cornerback James Bradberry will not play Sunday against the Browns after he was ruled a high-risk close contact for COVID-19. Bradberry’s exposure happened outside of the team facility and was not connected with offensive coordinator Jason Garrett — who tested positive and will be replaced by tight ends coach Freddie Kitchens for Sunday’s game against the Browns — but rather with a chiropractor who worked on him, a source confirmed to The Post.

The Giants did not have practice or in-person meetings Monday or Tuesday, but Garrett was on the field and in meetings with players and coaches Wednesday. Thursday’s practice was canceled “out of an abundance of caution” — depriving the Giants of a live look at how Daniel Jones is moving with hamstring and ankle injuries — and meetings were moved to Zoom, with Garrett’s input included.

Not only is Bradberry playing at an All-Pro level — he leads the NFL with 17 passes defended and the Giants with three interceptions — but also the rest of the cornerback depth chart is alarmingly thin. Isaac Yiadom, who went from starting to benched for three games to playing every snap the past six games, is now indispensable.

Rookie cornerback Darnay Holmes is trending toward missing a second straight game with a knee injury. Even if Holmes plays, all his experience is in the slot, so it would be a tall order to ask him to switch spots. The Giants can turn to Jarren Williams or Quincy Wilson off the practice squad — or ask Logan Ryan to return to his cornerback roots and replace him with safety depth in Xavier McKinney and Julian Love.

The soonest Bradberry can return to the Giants is Monday, if he continues testing negative. Garrett must be quarantined for 10 days.

The NFL reviewed electronic contact-tracing data and found no high-risk close contacts — defined as anyone who was within 6 feet of someone who tests positive for more than five minutes consecutively or for a total of 15 minutes — to Garrett. The test result came in Wednesday night and all coaches in the building immediately were isolated in offices.

“We always make it an emphasis on thriving on adversity,” coach Joe Judge said. “Something happens, we just keep moving on. We have plans in place. We have a process that we stick to for each game. What’s important right now is that we get all the players prepared to play Sunday night.”

Speaking Thursday morning, Judge said the Giants were “very fortunate” that Garrett’s positive test did not require anyone else to go into isolation. The good fortune didn’t last very long because, as Bradberry showed, outside factors are always at play in a non-bubble environment no matter how diligent the Giants are when gathered together.

Protocols include masks and a protective shield during walkthroughs, scattered meeting times to create even flow into the cafeteria and locker-room availability shifts.

“The one thing we’ve been told continuously throughout this whole process from the league is it’s all about spacing and avoiding crowds, and we’ve made an emphasis this entire year on doing that,” Judge said. “Throughout practice, we’re constantly moving around and keeping guys spread out.”

Kitchens will call plays against the team that gave him his first chance to be an NFL offensive coordinator in 2018 and that fired him as head coach after last season. The Giants (5-8) are one game behind Washington in the NFC East, though they hold the tiebreaker.

“Freddie’s experience in this league of calling plays and coordinating an offense is something that fits into what we’re doing right now,” Judge said. “We make sure that we talk continuously throughout the week, not only what we’re calling but why we’re calling it, so we understand situationally how the game plan has to unfold on the grass. We don’t want to play battleship football where we’re just calling plays and hoping to hit something.”

The Giants, during the summer, devised an emergency plan of coaches filling in for each other, but this is the first time a piece of that plan has been revealed. Multiple coaches call plays in practices as a way of development and to prepared them for this exact situation.

Ranked second-to-last in the NFL in total offense and scoring offense, the Giants are ahead of only the Jets in both categories. The formula for a four-game winning streak — relying on the defense to hold opponents to 20 points or less — just got more difficult without Bradberry and with one fewer practice to get his inexperienced replacements up to speed.

“This is something that we’ve been preparing for,” Judge said. “Missing a day of practice is not something unique in the league this year.”