There are a few different ways to double team in NBA 2K21 on PlayStation 4. One way is to use the "Double Team" button on the controller. This will cause two players on your team to join forces and try to block the ball from going into the other team's player. Another way is to use the "Triple Team" button, which will cause three players on your team to join forces and try to block the ball from going into the other team's player.