Truex felt his progress was stymied repeatedly by lapped traffic, blaming Roush Fenway Ford driver Ricky Stenhouse Jr in particular.
"It was just lapped cars," said Truex.
"It was a shame we got put in that position on that last restart but that's the way the caution fell.
"The #17 [Stenhouse] rode there in front of us forever and ever running the bottom [line], and I kept telling him I needed the bottom.
"These cars are just so bad in dirty air that he was holding me up really bad. Once I got around him, I got to the #2 car [Keselowski] in two laps.
"I just needed one more.
"Unfortunate. We had a great car, and the guys did a great job. I'm just a little upset. We had the best car. We probably should have won that one."
At one point late in the race it appeared that a penalty would prevent Truex from having a shot at the win.
Ryan Preece and BJ McLeod crashed in the pitlane on lap 272 of 325 in the middle of green-flag pitstops, which brought out a caution and jumbled the order.
Truex was one of the cars on the pitlane at the time and after the completion of his stop, NASCAR officials over the radio called out a penalty on his team for having a crew member over the wall too soon.
Serving the penalty would have put Truex at the rear of the field for the restart.
But when the race returned to green on lap 282, Truex remained lined up in fourth while several teams questioned over their radios why he was not dropping to the rear.
NASCAR's Twitter account even posted a tweet announcing the penalty but several minutes after the restart it was deleted.
Following the race, NASCAR officials said a review of the video footage of Truex's pitstop had convinced them to rescind the penalty because it was not completely clear from the camera angle that crew members had set foot in the pitlane too soon.
Although the penalty was rescinded, that decision was not publicly announced - resulting in the confusion.
Sunday's runner-up finish was still an important step forward from last week's Daytona 500, in which Truex was classified 35th having been caught up in the first of the red flag inducing multi-car crashes in the closing laps.
Truex added that he was "really proud of the team" for its "great rebound after last weekend", but said the defeat remained painful.
"They built a great race car here, and man, I could taste that one," he said. "I really wanted that first Atlanta win."
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