He'll join new head coach Steve Wilks and defensive coordinator Al Holcomb on the staff, per Art Stapleton of The Record.
It wasn't Arizona's only coaching move on Thursday. According to Rapoport, the Cardinals are also retaining "up-and-coming" quarterbacks coach Byron Leftwich, a "key move" for Wilks' staff. Rapoport added that "former coach Bruce Arians has been outspoken about Leftwich’s future as a coach."
McCoy, 45, brings head-coaching experience to Wilks' staff. He spent four seasons (2013-16) as the head honcho for the San Diego Chargers, going 27-37. He's also served as Broncos offensive coordinator twice (2009-12, 2017) and spent time with the Carolina Panthers (2000-08) as a quarterbacks coach, passing game coordinator and wide receivers coach.
From 2009 to 2017, his offenses with the Broncos and Chargers were top-10 in yards per game three times and top-10 in points per game twice, according to Pro Football Reference.
Like Denver in 2017, McCoy will head into the 2018 season with uncertainty at who will be orchestrating his offense. Carson Palmer retired and neither Blaine Gabbert or Drew Stanton is a franchise quarterback, leaving the team to address the position either via the draft or perhaps in free agency.
Whoever fills that position will have weapons, however, with running back David Johnson returning from injury and wideout Larry Fitzgerald still under contract (if he doesn't retire).
For a team that's gone just 15-16-1 the past two seasons and missed the postseason in both campaigns, however, how the Cardinals answer their vacancy at quarterback—and how quickly that player absorbs McCoy's offense—will decide whether the team can return to the playoffs.