GREEN BAY — Jared Cook no longer feels like the new kid on the block in the Packers’ offense

The eighth-year tight end has been immersed in the playbook since he signed as a free agent in March, discovering where he fits into the offense and picking up most of the signals.

Cook has seen 42 offensive snaps in the first two preseason games, catching four passes for 26 yards from backup quarterbacks Brett Hundley and Joe Callahan.

As comfortable as he feels, Cook knows the final exam that awaits him this Friday night when Aaron Rodgers makes his preseason debut against the San Francisco 49ers.

The tempo will pick up with the two-time MVP quarterback running the offense, challenging everything Cook has learned over the last five months.

“It’s going to be a good test to see how he runs the offense,” Cook said. “How he calls the plays and for me to keep up.”

Cook and Rodgers have developed a rapport with one another since Cook returned from the physically unable to perform list on Aug. 9.

The 6-foot-5, 254-pound tight end has been a popular target in the middle of the field and caught virtually every pass that’s been thrown in his direction over the past two weeks.

Cook already had an idea of the type of passer Rodgers was before he came to Green Bay, but he’s been impressed with the way the quarterback reads the defender and delivers the ball in the best spot possible for the receiver.

It’s uncertain how long Rodgers will play against the 49ers, but Cook knows how important it will be to capitalize on whatever snaps he receives with his new starting quarterback.

Cook feels like he has a good grasp of the offense. Now, it’s about fine-tuning all the details going into the regular-season opener against Jacksonville on Sept. 11.

“You’re the new kid on the block so you want to make sure that you’re pulling your weight and you’re doing what needs to be done to help make this team successful,” Cook said.

So is Cook feeling at home in the offense?

“Slowly,” he said with a smile.

Linsley’s long wait: Corey Linsley wanted nothing more than to be back out on the practice field when the Packers returned for the start of training camp on July 26.

However, the same hamstring that forced the third-year center out of most of the offseason program also has kept him on the physically unable to perform list for the last month.

Fourth-year offensive lineman JC Tretter had been taking the first-team reps at center in his absence, a prelude to Head Coach Mike McCarthy tabbing Tretter as the starter on Monday.

“There’s nothing I could do about it. I’m not out there practicing,” Linsley said. “They have to go with who’s practicing. JC is a great player and I think everyone knows that. I’m not out there competing with the guys.

“I’m confident in what I can do and I’ve shown what I can do. You just have to rest back on your confidence and get back healthy.”

Linsley first strained the hamstring during the workout portion of the offseason program, causing him to miss all of the team’s organized team activities and minicamp practices.

He remained optimistic about his chances of being ready for training camp before aggravating it during a workout in July prior to the start of camp.

Linsley said there’s no timetable for his return, though he doesn’t expect that the injury will require surgery.

 Only a great deal of patience.

“I’m not out for the year but it’s a matter of when the hell is this thing going to heal,” Linsley said. “It’s frustrating from that aspect but you just have to deal with it.”

First time for everything: Kenny Clark was standing on the sidelines at Nitschke Field on Tuesday afternoon when it finally dawned on the rookie first-round pick.

This was the first practice the 6-foot-3, 314-pound defensive lineman had ever missed in all of his years playing football after dropping out of Monday’s practice with a back issue.

“My first time ever missing a practice in my life, since elementary (school),” Clark said. “It’s difficult watching teammates out there practicing. You just want to be out there. First time I’ve ever missed practice, it’s crazy.”

The Packers were light on the defensive line Tuesday with Mike Daniels also missing practice with an illness.

Other stories:

Spofford: Rodgers fine with minimal preseason action

Spofford: Lots of deep balls in practice