ORCHARD PARK, N.Y. -- The Buffalo Bills held their second practice of a three-day rookie minicamp Saturday, with Sunday's final session closed to reporters.

There were 39 players on the field, but we'll focus our attention on the Bills' six draft picks, with a few additional observations from the 7-on-7 sessions of practice:

CB Ronald Darby: The Bills' second-round pick was used heavily during 7-on-7 drills in press coverage, a hallmark of Rex Ryan's defensive scheme. At 5-foot-11, Darby has some height but his speed is considered a bigger factor in his game. There weren't too many throws in his direction and some were misfires from tryout quarterbacks Brandon Hill (Monmouth) and Austin Trainor (West Georgia), so there wasn't much to evaluate on Darby's end. Undrafted receiver Andre Davis made an impressive catch down the sideline over Darby toward the end of Saturday's practice.

G John Miller: There was very little to evaluate on Miller, as the Bills did not go into 11-on-11 drills and therefore the offensive line never saw live action.

RB Karlos Williams: This is a passing camp, and without an offensive line, there isn't much to evaluate with running backs. What stands out is Williams' size. He is 6-foot-1 and 225 pounds and towered over the other running backs on the minicamp roster.

LB Tony Steward: The sixth-round pick arrived late to Friday's practice for unknown reasons but stepped in for 7-on-7 drills both Friday and Saturday. He was used as an off-the-line linebacker (the "Mike" and "Will" spots) and will be fighting for a role as special-teams contributor this summer.

TE Nick O'Leary: The Mackey Award winner from Florida State might have been the most frequent target in 11-on-11 drills. He had a notable catch up the seam Friday and added a few more Saturday, although he dropped a well-thrown pass Saturday. O'Leary is a throwback who doesn't wear gloves. Give that one a few months -- these Buffalo winters are a little harsher than those in Tallahassee, Florida.

WR Dezmin Lewis: At 6-foot-4, he was the tallest of six receivers taking part in the weekend's minicamp. There weren't any catches that stood out, and he saw only one rep Saturday against Darby, which ended in a pass being thrown to another receiver.

Undrafted rookies: The Bills signed 12 undrafted rookies (tackle Jermaine Barton, who was originally announced as joining the team, did not officially sign) and from this perspective, Davis stood out the most. His catch Saturday over Darby will catch coaches' attention, as will his size (6-foot-1, 211 pounds). Linebackers Andrew Hudson and AJ Tarpley got plenty of run in 7-on-7s, as did cornerback Cam Thomas and tight end Clay Burton. Linemen (both offensive and defensive) did not see live action this weekend.

First-year players: Several first-year players were eligible to participate in rookie camp, including linebacker Jimmy Gaines, safety Deon Broomfield, receivers Caleb Holley and Tobais Palmer and tight end Chris Manhertz. Palmer squared off with Darby multiple times in 7-on-7 drills, but the second-round cornerback won those matchups.

Tryouts: Former West Georgia quarterback Austin Trainor struggled toward the end of Friday's practice, possibly due to fatigue, causing the Bills to bring in former Monmouth quarterback Brandon Hill for Saturday's practice. Both quarterbacks were inconsistent Saturday, which is expected at this time of year but hampered the evaluation of both cornerbacks and receivers. The Bills had several tryout defensive backs in town, with former UTEP cornerback Wes Miller getting plenty of run at safety. At 5-foot-9 and wearing No. 35, he could easily be confused for former NFL safety Jim Leonhard, a favorite of Ryan.