The Broncos released a statement about the situation:
James Palmer of the NFL Network reported Modkins was "proactive" after being informed a family member tested positive and followed all of the league's coronavirus protocols.
The 49-year-old Texas native is in his third season coaching the Broncos' running backs. He's spent 26 years as an assistant at the collegiate and pro levels. His most prominent position was serving as the San Francisco 49ers' offensive coordinator during the 2016 campaign.
Meanwhile, Broncos running back Melvin Gordon III also isn't traveling with the organization to face New England while being treated for strep throat, per ESPN's Jeff Legwold.
Denver head coach Vic Fangio said Friday that Gordon was being treated for an "illness totally unrelated with COVID."
The Broncos' clash with the Patriots was delayed from Week 5 to Week 6 because of coronavirus concerns. New England quarterback Cam Newton and cornerback Stephon Gilmore were among the players to land on the reserve/COVID-19 list. They've both returned to practice.
Both teams had their bye moved up to Week 5 to accommodate the postponement and are scheduled to play 12 consecutive weeks to finish the regular season on time Jan. 3.
The lack of flexibility would make it difficult for Sunday's game to get moved again, and it's an issue that could become more prominent for the NFL over the next few months as teams work through their byes.
For now, the Broncos and Patriots are still slated to kick off 1 p.m. ET on Sunday at Gillette Stadium.