PITTSFORD, N.Y. - The Buffalo Bills are starting to get healthy again.

After their top five running backs and first three receivers sat out Thursday night in a 11-10 preseason victory at Cleveland, running back Fred Jackson and receivers Sammy Watkins and Robert Woods returned to the practice field Saturday.

"It's good to start getting some of these guys back," coach Rex Ryan said.

Jackson's return from a hamstring injury is critical at a position that has been decimated by injuries. The Bills are without leading rusher LeSean McCoy (hamstring), rookie Karlos Williams (undisclosed) and fourth-year pro Bryce Brown (hamstring).

Jackson is second on Buffalo's depth chart behind McCoy. He was not limited in practice Saturday and hopes to play next week against Pittsburgh.

"He looked pretty good," Ryan said. "I was happy to see him. He was doing more than I thought he was going to do."

Ryan reiterated Saturday that he is "cautiously optimistic" that McCoy will return in time for Buffalo's season opener against Indianapolis. McCoy was hurt in Tuesday night. Williams underwent an undisclosed procedure and is expected back for the season opener as well.

Watkins (glute) and Woods (undisclosed), Buffalo's top two receivers, took part in individual drills Saturday but did not participate in team drills.

Ryan said the Bills are expecting receivers Percy Harvin (hip) and Chris Hogan (ankle) to be ready for the season opener. Harvin had a platelet-rich plasma injection earlier this week to expedite the healing process and Buffalo expects him to play in at least one preseason game. Hogan was injured against the Browns, but Ryan was "cautiously optimistic" about his chances for the season opener.

Other injured players returning to practice Saturday included receiver Marcus Easley, defensive tackle Alex Carrington and linebacker Jimmy Gaines.

In other Bills news, Ryan said he had yet to decide who will start at quarterback against the Steelers. Matt Cassel, Tyrod Taylor and EJ Manuel have all performed well in preseason action as part of Buffalo's three-way quarterback competition but Cassel and Taylor are considered the front-runners for the job. Ryan has said that he will not reveal the winner of the QB competition until the season opener.

Cassel and Taylor worked with the first team in a low-key session Saturday that featured mostly scout team work.

Cassel did not play against the Browns but was efficient from the pocket in Buffalo's preseason opener against the Carolina Panthers. Cassel completed 7 of 8 passes for 45 yards in limited time against Carolina.

Taylor has showcased his abilities as a dual-threat quarterback this preseason. He has completed 12 of 18 passes for 114 yards while excelling as a runner with 10 rushes for 88 yards.

Manuel, a 2013 first-round pick, has worked mostly with the third team but has raised his level of play in Buffalo's first two preseason games compared to his up-and-down performances at training camp. Manuel has completed 13 of 22 passes for 188 yards and two touchdowns through two preseason games.

Ryan revealed Saturday that the Bills will likely keep all three quarterbacks on their active roster based on their play this preseason.

"All three of them are playing really well," Ryan said. "We said from day one that we'd keep the best 53 in our opinion and regardless of the position. But clearly you have three good quarterbacks, that's a high, high possibility."

Notes: The Bills signed receiver Austin Willis on Saturday. An undrafted free agent out of Emporia State, Willis was released by the Oakland Raiders on Aug. 18. He had 127 receptions for 2,002 yards and 18 touchdowns in college. To make room for Willis, the Bills waived defensive tackle Jeremy Towns.

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