Bills camp: What we've learned

After four days of training camp, Buffalo Bills players have the day off Thursday.

The team will remain at St. John Fisher College for training camp through Aug. 21, and don't play in their first preseason game until Aug. 11. Yet through the early stages of camp, we've been able to learn a few things about this team:

1. Manuel has started strong: In this space on Sunday, it was noted that if quarterback EJ Manuel struggled to begin camp, then veteran Kevin Kolb would likely need to take on a bigger role to maintain the improvement of the offense as a whole during training camp. Yet through four practices, Manuel has looked sharper. Head coach Doug Marrone said Wednesday that the defense will "start to throw more stuff at him," a sign that the coaching staff is pleased with Manuel's progress at this point. Look for the Bills to ease Manuel into the first-team offense more following Thursday's off-day.

2. Middle of roster still murky: From a talent standpoint, the Bills have some of the best players in their division at running back (C.J. Spiller), wide receiver (Steve Johnson), and cornerback (Stephon Gilmore). But at receiver, cornerback, and other positions, starting jobs are still up for grabs between large groups of young players. The incumbent starter at wide receiver, T.J. Graham, has looked solid through four days of camp, but rookies Robert Woods, Marquise Goodwin, and Da'Rick Rogers are all still far away from securing specific roles on the roster, and could still compete for the No. 2 job. At cornerback, Leodis McKelvin looks like he may be ready to settle into the No. 2 role after being eased into the start of training camp, but Justin Rogers could still push him for that job once he returns from injury. And at outside linebacker, Manny Lawson and Jerry Hughes are at the top of the depth chart, but Marcus Dowtin, Jamie Blatnick, and Kourtnei Brown are also in the mix.

3. Offensive line a concern: Marrone said on Sirius XM NFL Radio on Tuesday that depth along the offensive line is "a little bit of a concern," and added Wednesday that the Bills are looking to add someone to their competition at the open left guard spot. Through four practices, Colin Brown has seen the majority of first-team reps, while Doug Legursky began to see time with the top unit on Wednesday. The Bills have 17 offensive linemen on their roster, but Marrone's comments suggest that they may have more developmental players than those they can rely on for their 46-man game day roster. Meanwhile, Chris Hairston -- who looks to start at right tackle -- remains on the active/physically unable to perform list.

4. Recent history proves hard to shake: The Bills are on their fourth head coach in five seasons, while they also made a change at general manager this offseason. Marrone wasn't here last season when defensive end Mario Williams was slowed by a wrist injury, but the biggest news from a national perspective this week was Williams leaving camp to have his sore foot examined and some related tension between Marrone and reporters over the details of the injury. The feeling on this end is that Marrone, as a first-year head coach, was looking for a clean slate and should get one, but he is also inheriting a high-profile player in Williams, where every development will be under the microscope.

Roster move: The Bills signed cornerback Don Unamba on Wednesday evening, bringing their roster to 89 players. Unamba is an undrafted free agent out of Southern Arkansas who signed with the St. Louis Rams after April's draft.