No amount of precipitation, however, could dampen his spirits.
"I'm seeing some things that give me reason to be happy and excited about what we can be as a football team," Rivera said. "We got through all the installations that we planned, and we went through some situational football. We seemed to pick things up well."
Rivera and his staff will get one more chance prior to training camp to gauge their players' progress when the team holds its mandatory veteran minicamp beginning Tuesday.
Thursday, Rivera reviewed what he observed over three weeks of OTAs.
HAPPY CAM-PER: Upon declaring that the Panthers were ahead of schedule, Rivera singled out one player.
"The nice thing that you see is the progression of our quarterback," Rivera said. "I think Cam has done a really nice job. His rapport with the rest of the team has been really good."
"Coach Shula is stressing getting to the ball faster and keeping the defense on their heels," right tackle
Newton, of course, has something to do with that.
HAPPY RETURNS: Linebacker
Beason is coming back from knee and shoulder surgery, while Kalil is returning from foot surgery and Gross from ankle surgery.
"It's huge," Rivera said. "Any time you get your veteran leaders out there on the football field, that's a real big thing for the team."
All three participated in proceedings throughout OTAs. Beason was quite active from the beginning, while Kalil and Gross amped things up Monday.
"They came back Monday and kind of worked their way into it," Rivera said. "They did some stuff on the side, pushing and pulling each other, just to kind of see how it was. Once they felt comfortable, they started actually going through the drills and doing some of the teamwork.
"It's good to see that because it brings a little bit more cohesiveness to the offensive line."
NOT ALL SUNSHINE: While Beason, Kalil and Gross made their way back, a different trio was limited.
"You wish everybody would be healthy and could all take all the reps, but you can't always do that," Rivera said. "You also have to be careful to make sure we get through and get everybody healthy for training camp."
NEW AND IMPROVED: Rivera liked what he saw from his rookies during their minicamp nearly a month ago, and it was more of the same during OTAs.
"A big part of it is because of who they're working with now," Rivera said. "We had a bunch of rookies working together, and now we have a bunch of rookies mixed in with the vets. That's been really good."
While top choices
"We did the things we really wanted to do as far as installation, and we were able to incorporate the young guys into it," Rivera said.
FLASHERS: The strides made by young players weren't limited to the top draft picks.
Late in practices when time allowed, the Panthers added an "opportunity period" to allow youngsters to shine. The extra plays often featured quarterback
"He flashed," Rivera said. "(Running back)
QUICK HITTERS: Rivera said the battle for secondary spots remains wide-open, except in the case of free safety