A Boston Celtics mural in Massachusetts that was defaced by some jerks just got a facelift -- getting a fresh coat of Joe Mazulla's grill to hide all the vandalism!!
The OG art -- displayed in Cambridge -- featured Jayson Tatum, Derrick White, Jaylen Brown and Mazzulla ... but at some point during the Celtics' playoff run the last few weeks, it was destroyed by a curmudgeon.
In pics of the defacement, obtained by TMZ Sports ... you can see the individual scribbled, among other things, "F*** Celtics" all over the image of Tatum.
Dave O'Connor -- who goes by the artist name Croc Paints -- said he noticed the issues .. and jumped in to help fix them following the Celtics' big NBA Finals victory over the Dallas Mavericks.
Dave tells us ... the reason why he chose to paint just Joe on the cover-up was to show respect for the man who guided the team to its 18th title.
"The coach is the sixth man on the court," the artist said. "He played an enormous role in the success of the Celtics."
Dave was one of five artists who made the first mural to show their respect for their local team. While he was disappointed their first work was messed with ... he said he was happy to get another chance to re-paint Mazzulla, as he stated his first go-around wasn't his best piece of work.
The mural exists in an area known as Graffiti Alley ... an 80-foot-long wall that allows individuals to freely paint with no repercussions.
Michael Monestime, president of the Cambridge Central Square Business Improvement District, told us they hope to make a more permanent mural to honor the world champs ... as anything on the wall can be painted over at any time.
Monestime said he is unaware if Mazzulla knows of the mural's existence. They have reached out to the Celtics ... but have yet to hear back.