Head coach Lovie Smith said the injury would keep Reese out 4-6 weeks, which has been the standard timeframe for a return from a hamstring pull.
Part of the reason Reese wanted to rush back before he was healthy is because he didn't want to lose his starting job to Joe Odom.
Not only that, Reese doesn't feel his position on the team is secure.
"You're competing for a position and you can't really do nothing, you've just got to watch," Reese said. "It makes me want to comeback faster, but they (the training staff) say I can't comeback too fast because I might pull it again."
For a player that spent part of his rookie season without a team and other half between the 49ers and Bears practice squads the tease of starting in the NFL is tough to let go.
"It's upsetting, but than again I just have to worry about getting back. I can't really think what could have been," Reese said. "I know I can make an impact on this team - whether it's starting or on special teams."
At this point there are not plans to put Reese on Injured Reserve, but with Jerry Azumah and Rex Tucker eating up roster spots without being able to play until at least October the number of game day inactives is dwindling.
Last year injuries to other players led to Reese's release from San Francisco. The 49ers had a rash of ankle sprains on the offensive line and needed an extra spot to sign a backup to the practice squad.
Now injuries are impacting Reese's career again, but this time he's the one that needs to heal.
"Injuries can bump people, so I'm just going to have to get healthy," he said "They can't do anything with me when I'm in the training room."