Arnold Palmer’s chief rival and close friend said goodbye on social media.

“Arnold transcended the game of golf,” Jack Nicklaus writes. “He was more than a golfer or even great golfer. He was an icon. He was a legend. Arnold was someone who was a pioneer in his sport. He took the game from one level to a higher level, virtually by himself.”

Palmer popularized golf by coming of age on the links in the television age. Nicklaus, more than a decade younger, benefited by the trail blazed by the Pennsylvanian. Nicklaus called Palmer one of his “best friends. The Ohioan noted that he spoke to Palmer on his 87th birthday earlier this month but wished he could have had one last conversation with him in the two weeks after that.

Nicklaus wrote:

At this point I don’t know what happened, and I suppose it is not important what happened. What is important is that we just lost one of the incredible people in the game of golf and in all of sports. My friend—many people’s friend—just wore out. I know he was in Pittsburgh trying to find out how to make himself better. That’s what Arnold has always tried to do. He has always been a fighter and he never gave up on anything. He didn’t give up even now. Maybe his body did, but I know Arnold’s will and spirit did not.

Palmer bested second-place finisher Nicklaus, still an amateur. at the 1960 U.S. Open. Two years later in the Golden Bear’s rookie season as a pro he returned the favor to dramatically defeat Palmer at the U.S. Open at Oakmont. The pair finished one-two in majors on five occasions.