The Bills officially opened training camp Thursday afternoon with a two-hour practice session at an unseasonably cool St. John Fisher college.

“It was typical, other than not having pads on,” coach Chan Gailey said.

A few players were limited by injuries, and wide receiver Stevie Johnson was arguably the most impressive performer of the afternoon.

Who’s here: All 90 members of the team were in attendance, though not all of them fully participated. Prized free-agent addition Mario Williams received a loud ovation upon entering the field, hearing chants of “Super Mario” from eager fans. First-round pick Stephon Gilmore displayed good athleticism and already looks comfortable in the secondary. Second-year pro Chris Hairston worked with the starting unit at left tackle ahead of rookie Cordy Glenn, though Gailey has cautioned observers not to read too much into that. Buffalo used a rotation of receivers on offense, making it hard to draw any early conclusions about the No. 2 receiver battle. Mark Anderson started with the first team at right defensive end ahead of Shawne Merriman and Chris Kelsay.

Who’s not: Tight end Mike Caussin (PUP, knee) was the only Bill to not participate in any fashion Thursday. Cornerback Terrence McGee (knee), center Eric Wood (knee) and Torell Troup (back) were all very limited as they make their way back from injuries. Right tackle Erik Pears (hernia) was limited in team work.

Follow Bills reporter Mark Ludwiczak on Twitter @CBSSportsNFLBUF.