Harvey (0-2) gave up six runs in six innings, including a two-run homer to Braves catcher Kurt Suzuki in the first inning. Harvey's ERA now sits at 6.00.
"We haven't made that determination yet," Callaway said. "We'll see moving forward. I'm not sure what we're going to do."
Harvey wasn't receptive to a question about possibly moving to the bullpen.
"I'm a starting pitcher," Harvey said. "I've always been a starting pitcher. That's my mindset."
Harvey at least took pressure off the Mets' bullpen by making it through six innings. He retired 11 of the last 12 batters he faced and ended a streak of 12 consecutive starts, including his last nine starts of 2017, in which he failed to last longer than five innings.
"That last three innings I think I was able to break through that mental block I was feeling every time I went out there," he said. "I know that the results aren't there. I feel bad that it took me so long to figure it out."
The Associated Press contributed to this report.
Harvey roughed up in loss to Braves
Matt Harvey allows six earned runs as the Mets lose 12-4 to the Braves and suffer their first road loss of the season.