Buffalo Bills practice observations

PITTSFORD, N.Y. -- The Buffalo Bills opened training camp on Sunday evening, holding practice under the lights at Growney Stadium, on the campus of St. John Fisher College.

Following the rules of the collective bargaining agreement, players were in light shoulder pads. Full-padded practices can begin as soon as Tuesday.

Attendance report: Of the 87 players who have reported to training camp, 86 were in uniform for the session. Offensive lineman Chris Hairston, who is on the active/physically unable to perform list, was seen working out with the training staff on the sideline.

Mario Williams, Kyle Williams limited: The biggest news of the night was defensive end Mario Williams being held out of most drills with what head coach Doug Marrone called a sore foot. Marrone said after practice that Williams is being evaluated by the training staff. Meanwhile, defensive tackle Kyle Williams, who is recovering from Achilles surgery, did not take reps during 7-on-7 or 11-on-11 drills.

Chandler impressive in return: Tight end Scott Chandler, who underwent ACL surgery in January, was back on the practice field Sunday evening. Marrone said Chandler is still limited, but he drew cheers after beating his defender over the middle to make a catch during 11-on-11 work.

Kolb gets most first-team reps: Veteran Kevin Kolb saw the most action with the first-team unit at quarterback, although Marrone was quick to point out after practice that rookie EJ Manuel also took some snaps with the top unit.

As is to be expected, the results were mixed from both quarterbacks.

The good: During a drill early in practice where receivers matched up 1-on-1 against cornerbacks on deep patterns, Manuel showed good arm strength and touch, hitting receiver T.J. Graham in stride twice for would-be touchdowns. In 11-on-11's, Kolb matched Manuel with an impressive deep completion to wide receiver Marcus Easley.

The bad: Kolb was intercepted by safety Aaron Williams over the middle on his first pass of an 11-on-11 drill, while Manuel was picked off by safety Mana Silva later in the session. In 7-on-7's, safety Da'Norris Searcy snagged a tipped pass from Kolb, while in 11-on-11's, Manuel was part of a botched snap. In the 1-on-1 deep pattern drill, Manuel underthrew wide receiver DeMarco Sampson and was intercepted by cornerback Jumal Rolle.

Mixing and matching along D-line: With both Mario Williams and Kyle Williams held out of team drills, the Bills used a number of different personnel groups on their defensive line. The biggest takeaway was that Marcell Dareus saw limited action, especially with the top unit. It's unclear if he was nursing any type of injury. In his place, Alex Carrington and Jay Ross saw significant reps with top groups at linebacker and defensive back behind them. Meanwhile, Torell Troup and Alan Branch appeared to rotate at nose tackle during most drills.

Justin Rogers sees first-team action: Third-year cornerback Justin Rogers, who started just one game last season, lined up across from Stephon Gilmore with the top defensive unit during full-team drills. Ron Brooks manned the slot in sub packages, while Aaron Williams stepped in for Jairus Byrd at safety.

Brown gets nod at left guard: Despite facing competition from Doug Legursky and now Antoine Caldwell, veteran Colin Brown stepped in at left guard on Sunday evening, in place of the departed Andy Levitre. At right tackle, Erik Pears took Hairston's potential spot at right tackle, with Sam Young manning the second team. Thomas Welch took second-team reps at left tackle.

Marrone gets hands-on with O-line: It's been eight seasons since Marrone was last an offensive line coach, but he went back to his roots on Sunday evening. The Bills head coach spent significant time working hands-on with the offensive line in positional drills, coaching the unit on technique.

GOOD DAY AT THE OFFICE FOR: The safeties. Even with Byrd out, this group reeled in three interceptions.

BAD DAY AT THE OFFICE FOR: WR Robert Woods. The second-round pick dropped a well-thrown pass from Manuel during 1-on-1 drills, and had another from Kolb bounce off his hands in 11-on-11's.

WHAT'S NEXT: The Bills will be back on the practice field on Monday afternoon, from 2 to 5:10 p.m. ET.