ENGLEWOOD, Colo. — Payback is a… pain.

In 2017, albeit the first day of the year, Mike McCoy was donning Powder Blue & Gold—the then-San Diego Chargers colors.

Tom Telesco, the Chargers’ general manager, apparently didn’t like the way McCoy looked donning the lightning bolt—or his 28-38 record during his four-year stint leading the team—so he took actions into his own hands and fired the head coach immediately after the team’s final game.

Eight months later, McCoy will be at the the now-Los Angeles Chargers first game of the season, just on the opposite sideline, leading the Denver Broncos’ offense as their new coordinator.

In the eight short months since McCoy traded in the Powder Blue & Gold for the Orange & Blue in Denver, the Chargers have gone through significant changes as an organization—from hiring first-time head coach Anthony Lynn to moving from San Diego to Los Angeles. One aspect of the organization that didn’t change much from last season to this season, however, was the players that make up the Chargers’ roster.

That’s where McCoy’s greatest advantage comes into play.

According to research done by Over the Cap, the Chargers had the smallest turnover in the entire NFL from 2016 to 2017 in terms of “quality snaps.” Their definition of “quality snaps” essentially means players that played during the regular season. According to Over the Cap, the Chargers lost the fewest meaningful players from 2016 to 2017.

Long story short, McCoy knows the Chargers.

“He knows the personnel really well,” starting quarterback Trevor Siemian said in preparation for Los Angeles. “He knows the personnel really well, and that’s helped us out quite a bit.”

As the head coach of the Chargers for four seasons, McCoy should have a good grasp of the personnel on both sides of the ball, including special teams. But it isn’t just the personnel on the field that Denver’s offensive coordinator should have a solid grasp on—he knows the brains behind the offense very well as he was Ken Whisenhunt’s boss for two years.

Whisenhunt, Los Angeles’ current offensive coordinator, was hired two separate times by McCoy during his tenure with the Chargers to lead the team’s offense—first when McCoy became the head coach in 2013 and again in 2016 after Whisenhunt was fired as the Tennessee Titans’ head coach during the 2015 season.

Additionally, McCoy has had success in his career using knowledge of his former team to benefit his new team the following season. In 2013, McCoy’s first season as the Chargers’ head coach after leading the Broncos’ offense the year before, the 9-7 Chargers split the season series with Denver.

The 2013 Broncos not only were 13-3 with the No. 1 seed in the AFC West, they had the record setting Peyton Manning offense that was destroying opposing teams, accumulating margins of victory of 22, 18, 16, 32, 24, 23 and 20 points. The fact that McCoy’s just above average team went 1-1 against Denver was actually an impressive feat.

On Monday night, McCoy will have a much more manageable task—leading the 9-7 Broncos offense from a year ago against the 5-11 Chargers.

On Jan. 13, 2017, Denver hired McCoy for his ability to build a successful offense around any type of player—from Peyton Manning to Kyle Orton to Tim Tebow—but the cherry on top was his inside knowledge of a division opponent that the Broncos happen to play to kick off the 2017 season.