The Thunder struggled after losing All-Star point guard Russell Westbrook to injury in Game 2 of the first-round series against Houston.
After grinding its way through that series, the Thunder played Memphis close but lost four consecutive games to end the season in the second round a year after advancing to the NBA Finals.
“I have peace going through this run,” Durant said. “We really had to come together. We've really seen us grow as a group. The only way it would be frustrating is if we came in with an attitude because Russ was out and we didn't do that.”
The Thunder built a lead early, then saw it slip away with a 15-point second quarter.
Memphis led by as many as 14 in the third quarter before a wild play gave the Thunder a push.
A T-shirt thrown by Tony Allen seemed to breathe life into the Thunder midway through the third quarter but the boost was short-lived.
Allen was called for unsportsmanlike conduct from the bench after the shirt escaped his hand and landed at Derek Fisher's feet while Fisher missed a 3-pointer with about five minutes to go in the third.
Fisher was awarded the 3-pointer, and Durant hit the technical free throw to pull the Thunder within seven and fuel a streak that put the Thunder within two entering the third.
But the Thunder hit just 1 of 8 shots to start the fourth and Memphis stretched the lead back to double digits by the midpoint of the fourth before the Thunder made their final push.