Gordon, 27, announced Monday on Twitter that he'll be absent at the start of camp, which opens on Thursday in Berea, to focus on his treatment plan, but that he intends to be available for the start of the season.
But NFL spokesman Brian McCarthy told cleveland.com said ''there's no timetable for his return.''
In addition, McCarthy said that Gordon has not been suspended and that "we'll address the matter at the appropriate time.''
Under terms of collective bargaining agreement, McCarthy is not permitted to reveal whether or not Gordon violated the substance abuse policy again, which has been the subject of Internet rumors over the past month or so.
A source close to the situation said he's of the understanding that Gordon didn't fail a drug test, and if he had, he likely would have been suspended indefinitely. ESPN's Adam Schefter reported that Gordon didn't have any failed tests or setbacks, citing unnamed sources.
Gordon is in Stage Three of the NFL's Substance Abuse program and is subject to random testing up to 10 times a month. He announced his exit from the team on Twitter Monday morning.
"To my Cleveland Browns and NFL Family,
"I am reaching out to you all personally and letting you know that I am not only doing great physically but mentally as well. You will notice that I will not be in Cleveland for the start of training camp. Rest assured, this, too, is a part of my overall health and treatment plan. I appreciate the awesome support I have received from teammates, friends, fans, and the Browns organization. Just like you, I am excited to start the season and I have every intention of being ready and available to join my teammates soon to help bring winning football to our fans.
"With the help of the NFL, NFLPA, and the Browns' organization, I have been able to utilize the resources available to me that will ensure my well-being on and off the field. By continuing to follow the plan set up by our medical director and his team and taking this time before this season starts, we believe it will help me maintain the progress I've made for not only today but for many years to come.
"Thank you all for your patience, love, and support! Go Browns!"
Browns general manager John Dorsey also released a statement promising the organization will stand by Gordon while he gets back on track.
"We will continue to support Josh as he receives the care needed to maintain his progress,'' said Dorsey. "We're going to respect his privacy while he's away from the team. Josh will be placed on the non-football illness reserve list until he is ready to return.''
Gordon, 27, had been working out in Berea for most of the offseason, but recently left town to focus on his recovery. Sources say the Browns have no plans of parting ways with him in part because he's worked so hard since returning to the team in December.
Jimmy and Dee Haslam have always been supportive of Gordon and sympathetic to his illness, and have emphasized that his health and well-being are paramount.
Coach Hue Jackson, who seemed to slam the door shut on Gordon at the start of the 2016 season when he went back to rehab, now says he likes the receiver and understands Gordon was suffering from an addiction.
Gordon, who led the NFL with 1,646 yards in 2013, has been suspended for 56 of a possible 96 games since he was drafted in the second round of the 2012 supplemental draft, including 43 of his last 48 games.
During minicamp last month, Gordon declared the Browns' 2018 receiving corps the best in the NFL, especially with the addition of Jarvis Landry, and vowed to make a big splash this season. He also expressed gratitude for being in a good place.
"When I do find myself reminiscing of what's transpired in my life, really just blessed, man, and thankful,'' he said. "Right now for me it's a bunch of the small victories day to day, just being able to come to work. Like the little, little things.
"Having some structure in my life. You could be anywhere in the world doing something that you don't love to do, and I'm fortunate enough to be out here trying to give 100 percent at something I couldn't imagine myself having that much fun doing anything else. So it's a tremendous opportunity."
As for whether or not the Browns can depend on him, he said, "it takes effort and things being proven and that's something that can't be rushed. I'm not expecting anything, but I do know they support me, I know that."
He admitted that he never played a game sober before last season.
Gordon has recently posted social media stories of working out at the University of Florida in Gainesville. Last fall, he was reinstated to the NFL on a conditional basis by Commissioner Roger Goodell after spending 90 days in a Gainesville rehab facility.
Said Goodell: "At the end of the day (his career) will depend on Josh. His commitment to sobriety and to reaching his goals in football and beyond will determine his success. It ultimately is up to Josh."
When he returned to the club for the last five games, he caught 18 passes for 335 yards and a touchdown. The Browns are counting on him being their No. 1 receiver this season, starting opposite Landry.
In the meantime, they'll work out former Steelers receiver Eli Rogers likely on Tuesday, a league source confirmed. The workout was first reported by Mike Florio of ProFootballTalk.com.
In two accrued seasons, Rogers, who suffered a torn ACL in January, has 66 receptions for 743 yards and four TDs. He's obviously very familiar with Todd Haley's scheme from spending the past three seasons with him in Pittsburgh.
The Browns' other receivers this season include Corey Coleman, fourth-round pick Antonio Callaway, Rashard Higgins, Ricardo Louis, Damion Ratley and Jeff Janis.