After a rocky rookie season, Manziel entered a treatment facility late last month.
"Absolutely,'' Haslam told reporters when asked if he believes Manziel can get his act together off the field, according to Cleveland.com. "I ask that question a lot to our football people -- as recently as today. 'Do we still think he can be a starter in the NFL?' And the answer is consistently yes. I don't have the ability to judge that. I don't have that kind of technical expertise. Now, he's got to get himself straightened out and you've got to do that on the field, but yes.''
Manziel, the 22nd overall pick in the 2014 NFL draft, appeared in five games for the Browns (two starts), completing 18 of 35 pass attempts for 175 yards, zero touchdowns and two interceptions.
He was ruled out for the season finale with a hamstring injury, and was later fined an undisclosed amount by the team after failing to show up for treatment on the injury.
The Browns finished the season 7-9 despite after losing their final five games.
Manziel's struggles were magnified last month by an ESPN story that quoted anonymous Browns players who questioned his work ethic and off-field antics. One player was quoted as saying Manziel treated his rookie season as a "100 percent joke."
On Wednesday, Haslam again defended the Browns' decision to draft Manziel, despite previous reports of similar off-field issues while he was in college at Texas A&M.
"A few people didn't like him, but a lot of people really liked him, so I think it's way too early to give up on Johnny,'' Haslam said. "I do. I think it's way too early to give up on him. We certainly haven't given up on him and if it's two years from now and Johnny hasn't played any, or doesn't have his personal life together, that's different. But it's way too early. I think everybody's way too harsh. He's an easy guy to pile on and for everybody to give up on.''
- Mike Fiammetta