Fleener told The Athletic that he is still likely to play during the 2018 campaign, but that the symptoms are "still there, unfortunately."
"I'm just hoping it heals and gets better from time, I guess. I'd still like to play, but I have to get healthy first before I can even make that decision really. That's the frustrating aspect of it," he added. "The doctors aren't able to say, 'Oh, in four to six weeks, he'll be right as rain.' That's just not the reality with concussions. It's a frustration for every athlete and every doctor who treats them and every coach who has to coach them."
Fleener said he is uncertain if he can return to the field by the time training camp comes around.
"Ummm, I don't know," Fleener said. "That's a really hard question to answer, because, like I said, if you'd asked me a day or two after it happened, I would have said of course. But now I'm kind of taking it as the cliche goes, one day at a time. Tomorrow if I wake up and there are no symptoms, then we approach things differently."
The Saints released Fleener just two seasons into his five-year, $36 million contract with a failed physical designation. He sustained his fifth career concussion in Week 12 of the 2017 season.
Fleener recorded 72 receptions for 926 yards and five touchdowns in 27 games since joining the Saints as a free agent in 2016.
The 29-year-old posted a career-low single-season total in catches (22) to go along with 295 receiving yards and two scores in 11 games in 2017.
Fleener spent his first four years with the Indianapolis Colts after being drafted in the second round out of Stanford. He has 255 catches for 3,080 yards and 23 touchdowns in his six-year career.