BOSTON — The New England Patriots’ gentle giant has decided to hang up his cleats.

Patriots tight end Rob Gronkowski said Sunday that he is retiring from the NFL after nine seasons.

Gronkowski announced his decision via a post on Instagram , saying that a few months shy of his 30th birthday “it’s time to move forward and move forward with a big smile.”

“It all started at 20 years old on stage at the NFL draft when my dream came true, and now here I am about to turn 30 in a few months with a decision I feel is the biggest of my life so far,” Gronkowski wrote in his post. “I will be retiring from the game of football today.”

Drew Rosenhaus, Gronkowski’s agent, confirmed his client’s decision to retire.

The tight end, who turns 30 in May, leaves as a three-time Super Bowl champion who established himself as one of the most dominant players at his position.

But he has been dogged in recent seasons by back, knee, ankle and arm injuries that have limited his ability to stay on the field.

It led him to hint at retirement following New England’s Super Bowl loss to the Philadelphia Eagles to end the 2017 season and again last month after the Patriots’ Super Bowl win over the Los Angeles Rams.

In his Instagram post, Gronkowski thanked the Patriots organization, coach Bill Belichick and New England’s fans for their support during his nine NFL seasons.

“Thank you for everyone accepting who I am and the dedication I have put into my work to be the best player I could be,” Gronkowski wrote.

Gronkowski’s teammates almost immediately began to flood social media with well-wishes.

“Love you man!!” quarterback Tom Brady wrote on Instagram, along with an emoji of a goat to refer to Gronkowski as the greatest of all-time. “Couldn’t be a better person or teammate!!!!”

Gronkowski’s 12 career postseason touchdown receptions are the most by a tight end in NFL playoff history. His 81 career postseason catches are also best among tight ends.