The Giants planned to tinker with the offensive line but wound up making a big change instead.

Offensive line coach Marc Colombo was fired Wednesday and replaced by Dave DeGuglielmo — the latest and most significant shake-up at a position rotating seven players through five positions and drawing extra attention from head coach Joe Judge.

Judge brought in DeGuglielmo last week to go through COVID-19 testing protocols with the intention of adding him to the coaching staff as an offensive consultant, sources told The Post. When informed of the plan, Colombo balked at the idea of another coach looking over his shoulder, and their heated confrontation quickly turned salty and prompted Judge to make the bigger change.

The Giants denied a report that Judge and Colombo threw punches in a fight as “absolutely false in every way.” Judge spoke to the media Wednesday morning — before the change came to light.

“We appreciate what Marc has done,” Judge said in a statement, “but I felt like this move is in the best interest of the team.”

Judge originally interviewed Colombo and DeGuglielmo for one spot on his staff. He hired Colombo — who came from the Dallas Cowboys with offensive coordinator Jason Garrett — over his former New England Patriots colleague DeGuglielmo.

Wednesday’s news came as a big surprise to some within the organization because players liked and respected Colombo, seeing the former first-round draft pick and 10-year veteran as one of their own, a source said. Others saw the writing on the wall when DeGuglielmo arrived to ease the burden on Judge, who began taking a more active role than usual in coaching the offensive line during practice.

DeGuglielmo spent five seasons as a generally well-liked assistant offensive line coach under Tom Coughlin with the Giants. He is known for not biting his tongue with anyone — an approach that can rub some people the wrong way — and demanding a lot from young players.

DeGuglielmo has bounced around since leaving the Giants, including one year with the Jets in 2012 when the group ranked third-best in the NFL. He has worked under — and been fired by — two of Judge’s friends: Bill Belichick cut ties with DeGuglielmo after two seasons in 2015 and Miami Dolphins head coach Brian Flores let go of DeGuglielmo after last season.

Judge and Colombo had growing philosophical differences, but the original plan was not to fire Colombo until his reaction went against Judge’s team-first-at-all-costs philosophy.

Rookie first-round pick Andrew Thomas’ slow development has been an obstacle for the offense, with one offensive line expert after another pointing out flaws in his technique such as getting his shoulder pads too far out over his toes, playing with one foot off the ground and getting beat to the inside.

Thomas has allowed an NFL-high 44 quarterback pressures (six sacks) but has shown marked improvement over the last five games, when the Giants began rotating three tackles at two positions. They will begin doing the same at guard next week, having three rookies on the field together at times.

DeGuglielmo is the Giants’ fourth offensive line coach (Mike Solari, Hal Hunter and Colombo) since parting ways with Pat Flaherty, who held the job for the length of Coughlin’s tenure (2004-15). Recurring blocking problems are among the biggest reasons the Giants have had only one winning season since 2012.

Assistant offensive line coach Ben Wilkerson’s status was not affected by the change.

Colombo oversaw one of the NFL’s best offensive lines with the Cowboys. He could be more of a motivator, less of a teacher.

“It’s different,” Colombo said last week. “In Dallas, you had a couple of Hall of Famers, a perennial Pro Bowler, that type of deal. It was just about getting those guys the right amount of reps in every practice so they were ready and confident going into a game. Here, it’s every little tiny detail. You don’t take anything for granted.”

— Additional reporting by Paul Schwartz