What appeared to be a simple renovation of the Buffalo Bills' backfield this offseason could instead become a full-scale overhaul.

Two days before their trade with the Philadelphia Eagles for LeSean McCoy will become official, the Bills on Sunday agreed to a five-year, $40 million contract with the running back, locking him in as a centerpiece of their offense for the foreseeable future.

The deal includes $26.5 million in guaranteed money, second among running backs behind Adrian Peterson's $36 million guaranteed as part of his six-year deal signed in 2011. McCoy's contract will average $8 million per season, which is less than his previous deal (five years, $45 million), but the fourth-richest running back deal in the NFL behind Peterson, Kansas City's Jamaal Charles and Houston's Arian Foster.

Sources told ESPN's Josina Anderson that McCoy was initially unhappy with the prospect of joining the Bills, and giving McCoy this lucrative extension is a foolproof way to put a smile on his face and avoid any drama this summer. But it's also a significant chunk of change to fork over to a running back at a time when NFL teams are finding younger and cheaper options at the position.

The question for the Bills will be whether McCoy, who turns 27 in July, will be closer to Peterson and Marshawn Lynch -- two backs who have put up big numbers even as they approach age 30 -- or whether his production will decline, as it did for Chris Johnson and several others as they progressed into their late 20s.

McCoy is still one of the NFL's best runners, and extending him frees up cap space for Buffalo this offseason. But the long-term risk for the Bills is greater now that they've agreed to this new deal.

Surprisingly, the Bills aren't stopping there. Trading for McCoy could be just the first move in an overhaul of the entire offensive backfield.

The Bills have expressed interest in signing former New York Jets running back Bilal Powell, a source told ESPN's Dan Graziano. The New York Daily News reported Sunday that the Jets believe Powell is leaning toward joining the Bills.

It's easy to connect the dots between the Bills and Powell. He was a complementary piece for the Jets when current Bills coach Rex Ryan and current Bills running backs coach Anthony Lynn roamed the Jets' sideline. At 26, he has tread left on his tires.

Signing Powell would crowd a Bills backfield that will lose C.J. Spiller to free agency this offseason but still includes Fred Jackson, Anthony Dixon and Bryce Brown.

If Powell chooses the Bills over returning to the Jets, it would likely mean some sort of assurance from the Bills' coaching staff that he would receive a sufficient amount of carries behind McCoy.

That could have a trickle-down effect on the rest of the Bills' backs. First, it could mean Brown -- whom the Bills acquired for a fourth-round draft pick last May -- could be pushed off the roster.

It could also be bad news for Jackson, who turned 34 in February.

Jackson told ESPN last month that he wants to play three more years in the NFL. But with the Bills' interest in signing Powell, it's fair to question whether those three years come with the Bills. The fact that they're even considering adding another running back beyond McCoy signals some doubts about Jackson, who averaged 3.7 yards per carry behind a poor offensive line last season.

Jackson has one year left on the contract he signed with the Bills last summer. He'll be paid $2.73 million, but there is no guaranteed money, meaning the Bills could release Jackson at any time before the start of the regular season without penalty.

Is such a move imminent? No. But the Bills appear to be in the middle of a remake of their offensive backfield; one that clouds the future of Jackson and others.

Stay tuned.