Gronkowski led the Patriots with 1,084 yards and eight touchdowns past year across 14 games.
Gronkowski declined to return calls from the Lions.
This all went down during the weekend of the draft - per Schefter the two clubs "were deep into trade discussions last offseason that peaked during the week of the draft, when the teams almost completed a blockbuster trade".
The five-time Pro Bowler met with the Pats and the two sides agreed to a plan that would allow Gronkowski to continue to play for the team and talks with the Lions were dropped. Other players included in the deal were not identified. It was nothing personal against the Lions or their new Coach Matt Patricia, the Patriots' former defensive coordinator.
Gronkowski, 29, has nine catches for 138 yards and a touchdown in the Patriots' first two games this season.
The Packers already got a taste of Mack, who was traded to the Chicago Bears the week before the season opener. He was removed from New England's injury report Friday after being limited in Wednesday's practice because of an ankle injury.