On the day the Jets traded for quarterback Aaron Rodgers in April, Randall Cobb posted a workout video to Instagram.

Cobb, a receiver, had spent 10 of his 12 N.F.L. seasons as Rodgers’s teammate and close friend with the Green Bay Packers, but was by then a free agent recovering from surgery on his right ankle to clear bone spurs. Cobb said he had preplanned to publish the video to showcase his health as teams looked to round out their rosters.

But, Cobb said, other players teased him for the timing of the post because it appeared to signal that he wanted to join Rodgers without blatantly saying so.

“It just happened to be on the same day,” Cobb, smiling, said in an interview last week at his locker in the Jets’ practice facility.

Cobb, 33, had been considering retirement when the Jets signed him to a one-year contract just over a week after the Rodgers trade, and after the quarterback had recruited him. Reunited in New Jersey, Cobb has been a gauge of Rodgers’s moods and a messenger to Jets teammates for how to keep him happy.

That value was on display in a recent episode of “Hard Knocks,” the HBO documentary series, as Cobb huddled the Jets’ receivers after a poor practice and warned the group that Rodgers would not tolerate continued errors.

“If he don’t trust you, he’s not going to throw you the ball, I can promise you that,” Cobb said. “If he don’t trust you — he do not like throwing interceptions — so if he can’t trust that you’re going to run the right route, he’s not going to throw it.”

“How he communicates to those guys has been amazing for them in that room,” said Nathaniel Hackett, the Jets’ offensive coordinator. Hackett held the same position for three seasons with the Packers, where he coached Cobb and Rodgers in 2021. “I think they are only going to get better, just with him being in there and the fact that we get to have him out there playing for us is great.”

There are few people who know Rodgers better on and off the field. Cobb has long been one of the quarterback’s most trusted passing options, usually catching tosses out of the slot position. Rodgers was a groomsman at Cobb’s wedding in 2017 and is godfather to one of his two children.

Cobb and Allen Lazard, 27, another former Packers receiver, are expected to play complementary roles in the Jets’ offense, whose success will depend on the development of receiver Garrett Wilson, 23, last season’s offensive rookie of the year, and Mecole Hardman, 25, a free-agent addition who spent his first four N.F.L. seasons with Kansas City. Cobb said he could act as an intermediary and help teammates adjust to their new quarterback’s personality and tendencies.

“I try to be the bridge of communication,” Cobb said. “We’re all visual and audio learners, and just being able to see if a guy needs help, you can help them understand it in a different way.”

Cobb said he has tried to preach to the receiving corps the importance of nonverbal communication before the snap, and emphasized that they should understand each component of a play instead of just their role in it. For example, on a goal line play last December, the rookie Christian Watson missed a hand signal from Rodgers, ran the wrong route and missed out on an easy touchdown reception against the Los Angeles Rams. Cobb said receivers earn Rodgers’s favor by being in the right place at the right time.

“He’s just very detail-oriented,” Cobb said. “He does a great job of taking care of the ball, and if we’re not on the same page, that can lead to two interceptions and puts us behind the eight ball and a chance to win the game.”

Rodgers, though, has worked to form connections with teammates without Cobb’s direct help. He said in July that he ate lunch at different tables throughout the week so as not to sit with the same players, adding that he visited different areas of practice when he was not taking reps to familiarize himself with different position groups. Wilson said Rodgers has been talkative and approachable, but he also welcomed learning from Cobb.

“I’ve just been trying to take everything I can from Randall,” Wilson said Friday in a news conference. “He’s a perfectionist when it comes to everything off the field.”

Having Cobb around has also been a boon to Rodgers in other areas. Playing together in a new city, the pair, along with other teammates, have been intentional about bonding at social events. Last week, Cobb, Rodgers and tight end C.J. Uzomah attended a tennis match at the U.S. Open, and the three have gone with other teammates to Broadway shows.

Rodgers and Uzomah attended the Tony Awards in June, and the quarterback watched a Knicks playoff game with cornerback Sauce Gardner from courtside seats in May.

Cobb said the vibrancy and bustle of playing for the Jets offered a different experience than Rodgers had been exposed to during the football season. After Packers games, for instance, Cobb said he and his family would normally order pizza because most other restaurants were closed. Not so in the New York metropolitan area.

“It’s not like the N.F.L. life that you imagine in your mind,” Cobb said of living in Green Bay, Wis. “I think that he’s able to live and enjoy life with a different perspective that he hasn’t had in his career yet.”