A source told ESPN that Gronkowski reported with the rest of his teammates and is continuing to work behind the scenes as the club takes a cautious approach with an undisclosed physical ailment that isn't considered a long-range concern.
Gronkowski has been showing up for workouts all offseason. He also wasn't on the field in the last practice open to reporters, a voluntary organized team activity on May 26.
It has been commonplace for the Patriots to hold back Gronkowski in recent years after he injured his forearm and knee in 2012 and 2013, respectively. Over the past two seasons, Gronkowski has missed just two games because of injury.
Head coach Bill Belichick was predictably evasive when asked about Gronkowski's whereabouts Tuesday.
"There are a lot of players that were not on the field," he said. "They were doing other things."