Full disclosure: This is a totally unconfirmed rumor. It may very well be false. But if it were true, this would easily be the worst thing Garnett has ever said on the court. Here it is:

The Timberwolves faced the Spurs at the Alamodome for a first round playoff game on May 9, 1999. At some point during that game, Garnett told Duncan “Happy Mother’s Day, M***********” as the Spurs legend lined up for a free throw.

Duncan’s mother passed away of breast cancer, one day before Tim’s 14th birthday in 1990.

While this incident has never been confirmed, what is confirmed is that Duncan hates Garnett, according to a 2012 Sports Illustrated profile:

“In fact, Duncan hates Kevin Garnett. Hates him the way liberals hate Sean Hannity. This information comes from very reliable sources, who talk about how KG has made a career of trying to punk Duncan, baiting him and slapping him and whispering really weird smack into his ear. They talk about how funny this is, because the worst thing you can do as an opponent is piss off Duncan. Then, as Malik Rose says, "he f------ destroys you." Duncan's lifetime numbers versus Garnett's teams, by the way: 19.4 points per game, 11.6 boards and a 44-17 record, including the postseason.
Duncan is diplomatic about the topic. Asked if perhaps all those years battling Garnett have softened his feelings for the man, led to a Magic-Larry type of kinship, Duncan leans back on the couch in his hotel room and grins. There is a pause. A longer pause. Finally he says, "Define kinship.”

Duncan and Garnett will both likely be inducted to the Hall of Fame in 2021 when they will be on the ballot for the first time. This could make for an awkward ceremony in Springfield.