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So much for the Buffalo Bills' plan to ease rookie C.J. Spiller into their running back rotation.

With starter Fred Jackson out at least a month with a broken left hand and backup Marshawn Lynch limping on a sore ankle, Spiller's going to have to hit the ground running — and receiving and returning punts — for the remainder of the preseason at the very least.

"I haven't talked to the coaches at all, but I've just got to be ready for however many reps I'm given," the first-round pick said Monday. "It doesn't matter to me if I have to play the whole game. This is football. This is what I love to do."

Spiller, drafted ninth overall out of Clemson, spoke after the Bills returned to training camp for their first practice since a costly 42-17 preseason-opening loss at Washington on Friday. Lopsided score aside, the injury toll on the Bills' backfield was more significant.

Wearing a cast covering most of his lower left arm, Jackson revealed that he will miss four to six weeks after breaking a bone in his hand on the second play from scrimmage.

Jackson hopes it'll be closer to four weeks, which would put him in a position to be ready for Buffalo's opener Sept. 12 against Miami.

He was hurt at the end of a 7-yard run while attempting to brace himself as he was being pulled down by the facemask by safety Kareem Moore, who was penalized on the play. Tests taken over the weekend confirmed that Jackson broke the fourth metacarpal bone.

"It's a huge disappointment," said Jackson, who finished last season as the Bills' starter and led the team with a career-best 1,062 yards rushing. "Standing on the sideline, you can't do much to help your team."

Lynch, who split the starting duties with Jackson last season, was hurt later in the opening drive, at the end of a 20-yard run that was negated by an offensive holding penalty.

Following the team's evening practice, coach Chan Gailey said he expects Lynch to miss two to three weeks, but noted he could be ready for Buffalo's preseason finale at Detroit on Sept. 2.

"Any time you lose two really great players it's a setback," Gailey said. "That part is tough, but it happens all the time. It's part of this business. You've got to deal with it and go on."

The Bills host Indianapolis at Toronto on Thursday.

Rather than using Spiller as the featured running back, the Bills' intention was to use his dynamic potential in several roles, from splitting out as a receiver to using him in a two-back formation alongside either Jackson or Lynch.

Gailey said the injuries will prevent the team from working on those plays and formations until at least Lynch returns.

Gailey did see one benefit, noting Spiller will get additional playing time and allow him to catch up after he missed the first seven days of training camp before signing his contract on Aug. 6.

Spiller will now be sharing the duties with Chad Simpson, who appeared sparingly in 25 games with Indianapolis over the past two years, and undrafted rookie free agent Joique Bell. Buffalo added another running back on Monday by signing Andre Anderson, an undrafted rookie free agent out of Tulane.

"Now I'm the next guy in line to try to step up into those big shoes and try to fill them for this preseason," Spiller said. "I'm going to try to do my best."

The ACC's player of the year last season, Spiller is a speedster who proved to be a versatile threat as a running back, receiver and on special teams at Clemson. He finished his four-year college career with 51 touchdowns, including 32 rushing, and joined Reggie Bush in becoming only the second player to have 3,000 yards rushing, 1,500 yards in kickoff returns, 1,000 yards receiving and 500 yards in punt returns.

Against Washington, Spiller had four carries for 16 yards.

"I feel a whole lot more comfortable going into this game than I did last week," Spiller said. "I've just got to step up."

Jackson is confident Spiller can handle the extra workload.

"It's tough, but that's why you've got to stay ready," Jackson said. "He's preparing to be the No. 1 back while we're gone, so hopefully he can pick up things and keep the offense moving."

Notes: WR Marcus Easley missed both practices because Gailey said the rookie fourth-round draft pick is preparing to have surgery to repair an injury to his left leg. Gailey said it's too early to determine how long Easley will be out. ... The Bills also signed WR Aaron Rhea, an undrafted rookie free agent out of Stephen F. Austin, and placed LB Ryan Manalac on waived/injured. ... Rookie third-round pick DE Alex Carrington did not practice after he was hurt early in the third quarter on Friday. ... DE Spencer Johnson returned to practice for the first time since hurting his leg on July 30, the second day of training camp.