Durant returned from a right calf strain that had kept him out for a little over a month. He played 12 minutes before exiting in the second quarter with what was later confirmed to be a new injury.
The Warriors announced Durant will undergo an MRI Tuesday, but president of basketball operations Bob Myers said it's an Achilles injury without offering further specifics.
Cousins knows Achilles injuries better than most. He missed almost a full year after rupturing his in January 2018.
While it's too early to tell whether Durant will be out for a similar amount of time, he appears likely to miss the remainder of the Finals.