PITTSFORD, N.Y. (AP) — The revamped group of Buffalo Bills receivers is suddenly down a key addition with Jordan Matthews sidelined indefinitely because of a chip fracture in his sternum.

The Bills list Matthews as week to week, and general manager Brandon Beane told The Associated Press on Monday he's "hopeful" the newly acquired player will be ready for the season opener in four weeks. Beane said the team's medical staff is "still figuring it out," because the timetable for recovery depends on how quickly the bruising subsides and the bone heals.

Matthews hurt the mid-chest bone that connects his rib cage on Sunday, during his first practice since joining the team in a trade with the Philadelphia Eagles. Matthews finished practice before being escorted off the field to be evaluated.

It's unclear when Matthews was hurt, though he did fall hard along the sideline while attempting to make a leaping catch in one-on-one coverage with cornerback Shareece Wright during a team drill.

The Bills are counting on Matthews to fill Sammy Watkins' spot after he was dealt to the Los Angeles Rams for cornerback E.J. Gaines and a second-round draft pick in a separate trade on Friday. Buffalo gave up starting cornerback Ronald Darby to acquire Matthews and a third-round draft pick from Philadelphia.

Coincidentally, one of the reasons the Bills considered Watkins expendable was because of a rash of injuries that have hampered his production during his three seasons in Buffalo. That included a broken left foot that forced the 2014 first-round draft pick to miss eight games last season.

Aside from the draft picks, Matthews was the key addition to address Buffalo's more immediate needs on what is now a retooled group of receivers. Buffalo lost starter Robert Woods and speedster Marquise Goodwin in free agency this past offseason.

The Bills were looking for Matthews to play alongside Anquan Boldin , who was signed last week, and rookie second-round draft pick Zay Jones. Also competing for jobs are Walt Powell and offseason free-agent additions Andre Holmes and Rod Streater.

Though not considered as dynamic of a deep threat as Watkins, Matthews has been consistent in his first three seasons with the Eagles. He was Philadelphia's most productive receiver with 2,673 yards and 19 touchdowns. He became just the fifth NFL player to top 65 catches and 800 yards in each of his first three seasons.

Matthews would have made his preseason debut Thursday against his former team.

Dr. Matthew DiPaola, a University at Buffalo assistant professor of orthopedics and sports medicine, said a chip fracture involves a small sliver or shell breaking off any bone in the body.

Though he's not treating Matthews or seen the player's medical records, DiPaola said chip fractures don't usually require surgery and are treated through rest and anti-inflammatory medicine. A chip fracture to the sternum could cause a person discomfort when breathing, he said.

NOTES: CB Kevon Seymour returned after missing a week of practice with a foot injury. ... DL Adolphus Washington did not finish practice due to back spasms. ... The Bills will hold their final day of practice at training camp on Tuesday.

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