Royce Young of ESPN.com reported the news, noting the reigning NBA Finals MVP claimed he made an honest mistake.
Sports Illustrated captured the social media exchange, where Durant liked a comment that said of his time in Oklahoma City: "The problem was Westbrook. They had a good ass team."
Durant and Westbrook were teammates on the Thunder from 2008 through 2016, when the former left via free agency to join the Warriors. Durant won the championship in his first season with Golden State after failing to lift the Larry O'Brien Trophy in Oklahoma City even though he and Westbrook made four Western Conference Finals and the NBA Finals.
This isn't the first time Durant has generated headlines this season because of his social media use.
Durant responded to criticism on Twitter in September, although Kyle Boone of CBS Sports noted "it appears he did one of two things: responded to a hater in the third person, or, most likely, attempted and failed to use a faux account to defend himself."
The comments Durant made then indicated the Thunder would be in trouble if they took Westbrook off the team, contradicting the notion the point guard was the problem, which was expressed in the Instagram comment the Warriors playmaker liked Monday.
Westbrook and Durant are each battling in the first round of the playoffs, with the Warriors leading the San Antonio Spurs 3-1 heading into Tuesday's Game 5 and the Thunder trailing the Utah Jazz 2-1 before Monday's Game 4.
They wouldn't face each other until the Western Conference Finals if they each advance.