As New England Patriots tight end Rob Gronkowski weighs his future, sources close to him say he has recently expressed that he is more likely to continue his football career than retire at 28 years old.

Sources say Gronkowski still hasn't made a decision. But despite serious considerations since the end of the season of retiring because of physical and mental fatigue, sources say Gronkowski is "pretty certain" he'll come back as long as Tom Brady remains with the team.

However, this dose of good news for Patriots fans comes with some dilution: Lingering frustrations remain between Gronkowski and head coach Bill Belichick, along with others in the Patriots organization, according to sources close to each side. Whether those frustrations on either side will impact Gronkowski's return to the team remains the final piece to this unfinished puzzle.

For Gronkowski, the physical anguish of the 2017 season, which led him late in the regular season to tell people that he was likely to retire, was paired with some mental fatigue from the high-strung culture within the Patriots organization, sources said. Nothing has occurred since the end of the season to convince him that is going to change -- and Gronkowski knows he'll need to be ready for a similar toll on his mind and body if he returns in 2018.

Although Rob Gronkowski is "pretty certain" he'll be back with the Patriots as long as Tom Brady stays, lingering frustrations remain between Gronkowski and coach Bill Belichick, along with others in the organization, according to sources. AP Photo/Chris O'Meara

For Belichick, since the season's end, sources say he has expressed frustration with those close to him about Gronkowski, specifically questioning whether he remains "all-in," a critical aspect of Belichick's blueprint for success.

Examples of Belichick's frustrations are as nuanced as his discontent with Gronkowski's message in a recent Instagram post regarding former Patriots wide receiver Danny Amendola, who left New England to sign a contract with the Miami Dolphins. Beneath a video of him hugging Amendola that Gronkowski posted on March 14, he wrote, in part, "Be FREE, Be HAPPY."

Should the offseason continue to create a sense within Gronkowski that he is fully committed to football, many close to Gronkowski and Belichick say they believe the friction between the two will ease. Although the discord should not be discounted, as one source explained, it should not be viewed as irreconcilable.

For now, the situation surrounding Gronkowski continues to percolate behind the scenes while all sides remain generally vague in public forums. With the NFL draft still more than three weeks away, there is time for the situation to rectify itself.

Should the silence linger deeper into April, however, all possibilities remain on the table.