Gronk doesn't want to leave Tom Brady's side, and he threatened to retire as a result.
ESPN's Adam Schefter reported on Sunday morning that the trade was nearly consummated before this year's draft, but Gronkowski refused to answer the Lions' phone calls.
Gronkowski has spent his entire nine-year career in New England, winning two Super Bowls. In that time, however, he's played a complete 16-game campaign just twice and 15 games two other times.
Nonetheless, Gronk is a four-time All-Pro and has formed a strong bond with Brady, even following his quarterback's TB12 training methods.
The Patriots restructured the tight end's contract ahead of the 2018 season, adding $4.3 million in incentives.
The Lions, coached by former Patriots defensive coordinator Matt Patricia, managed to shut down the Brady-Gronkowski connection on Sunday, limiting Gronk to four catches for 51 yards.