GREEN BAY -- The Packers' organized team activites (OTAs) are underway this week, and with the changes at offensive and defensive coordinator, Head Coach Mike McCarthy said the players are dialed in from the start.

"The energy in the building is significant since the change. I would say that's normal," McCarthy said prior to Tuesday's practice, the second of 10 OTA sessions over the next three weeks. "The first OTA, my recollection is it's always high energy (with the mindset) 'it's about time' to get out here and play simulated football.

"It's really the true opportunity to build and to grow."

Offensive coordinator Joe Philbin and defensive coordinator Mike Pettine have their playbooks to install, and the OTAs are the first run-through of those installations. McCarthy was pleased with Monday's first workout, which focused primarily on the passing game. He noted there were no pre-snap penalties, which is a reflection of the players' early focus.

No specific injury updates were given, other than McCarthy saying all players are participating at some level, in the classroom at a minimum. On-field work is coordinated by the medical staff based on players' rehab schedules.

OTAs also present the first opportunity for the rookie class to do 11-on-11 work with the veteran players, though no pads will go on until training camp.

"The most important thing is for the rookies to keep up," McCarthy said, referring to the mental challenges with learning the playbook. "Because once training camp gets here, it's a whole different ballgame."

Packers.com will have more following practice and locker room interviews.