The 21-year-old was selected in the first round of the 2014 Draft and was expected to win the battle to become Mike Pettine's side's signal caller for their opener against the Pittsburgh Steelers.
However, poor performances in training camp and pre-season have led Pettine to pick the veteran over Manziel.
"I didn't necessarily feel like I was ready, and I felt like there were steps that I needed to take and I need to take to move forward and get better," Manziel told reporters.
"I wouldn't say necessarily lights a fire. It's disappointing. Obviously I didn't want this to be the outcome. Down the road as the weeks continue to go on I'll get better, so does it light a fire? I don't really know if it does or not."
The Browns open their 2014 campaign against the Steelers on September 7.