Jackson expressed his unhappiness following practice Monday, saying he feels underappreciated and uncertain of where he stands.
"I feel like a No. 1 back," Jackson said. "I feel like I should be treated like one, know what's going on, know where I stand and what the situation is."
He spoke after the Bills returned to practice following a 24-10 preseason loss at Denver in a game second-year running back C.J. Spiller started and received most of the playing time with the starters.
Jackson said his concerns were not directed at Spiller, but instead at "everybody."
This isn't the first time Jackson said he's felt this way.
He led the Bills with 1,062 yards in 2009, only to have the team select Spiller with the ninth pick in the draft the following spring. Last year, Jackson opened the season third on the team's depth chart behind both Spiller and Marshawn Lynch.
After Spiller sputtered and Lynch was traded to Seattle, Jackson regained his starting job to once again lead the Bills with 927 yards and five touchdowns.
"It's been like this for two, three years," Jackson said. "I've got to keep fighting for what I feel like is my job."
His contract is also a sticking point, given that Jackson feels underpaid for his production. He's entering the third year of a four-year contract worth about $7.5 million.
The one thing Jackson won't change is how he plays.
"I'll continue to show up on the field," he said, "make plays when I get that opportunity."
Coach Chan Gailey said he considers both Jackson and Spiller to be starters, and added he feels Jackson is "a little bit ahead."
What took Gailey by surprise was learning Jackson felt underappreciated.
"I would hate for somebody to feel that way because it's not true from my standpoint," Gailey said. "Nothing's changed with our thoughts with Fred and where Fred is with our football team. He's a major part of what we're trying to get done here."
Against Denver, Spiller received the ball on four of Buffalo's first six plays from scrimmage and finished with six carries for 10 yards and two catches for 11 yards. Jackson had four carries for 34 yards and added 13 yards on two catches.
An undrafted free agent out of Coe College, Jackson has been the Bills' most consistent offensive player the past two seasons. He's a rugged runner, a capable receiver and has also produced as a returner on special teams.
In 2009, Jackson led the NFL with 2,516 yards when factoring in his 1,083 yards in punt and kickoff returns. He also became the first NFL player to have more than 1,000 yards in both rushing and kickoff returns.
A two-year starter, Bell was beaten at least twice against Denver, including one that led to an 8-yard sack. The potential switch comes a week after Levitre was briefly demoted in having to share starting time in practice at left guard with Chad Rinehart.
Gailey hasn't ruled out the possibility of having Rinehart start at guard and Levitre take over for Bell at tackle.
Gailey also announced that receiver Donald Jones and rookie running back Johnny White are expected to miss the remainder of the preseason with head injuries after both players were hurt against Denver.
White was hurt when he was slammed to the turf when tackled by Broncos linebacker Mario Haggan. White was wheeled off on a stretcher and briefly hospitalized but traveled home with the team.
Jones was shaken up while attempting to make a catch up the sideline, when safety Rahim Moore led with his right shoulder in hitting the receiver's helmet. Moore was penalized 15 yards for the hit.
"It wasn't pretty," Jones said, noting he only watched a replay of the hit earlier in the day. "It's football. Whether he thought it was legal or illegal, it is what it is. We play them again in December. So, we'll see."
Jones said he feels fine, adding he's not suffering from any post-concussion symptoms.
Receiver Naaman Roosevelt will also miss a few weeks with an ankle injury.
Without going into detail, Gailey said veteran linebacker Chris Kelsay had "a procedure" that will force him to miss a few days.