The first Jounin they trained with was Gai. They were told by the Hokage to show up at training ground 5 at a ridiculously early time in the morning. Not by their standards, team 7 had long since given up on the normal hours meant for training, the nightmares had seen to that.
They showed up on time and watched bemusedly as Gai and Lee introduced themselves in their exuberant fashion. Gai's declaration that he'd train his rivals's Genin when Kakashi could not do it himself helped them warm up a little to the intensely effervescent man. They had not known Kakashi had a rival, much less a friend as this guy seemed to be. He didn't look much like a ninja, but once training began, their doubts were quickly dispelled.
Sakura who had taken to speaking as little as possible and hiding behind Naruto and Sasuke in order to avoid people changed completely when it was time to train.
They threw themselves into Gai's training regime fully. They had begun to develop a relationship with the kind of training that left their bodies battered, it was what chased away guilt and anger and brought some measure of peace and sleep. So they fully embraced the laps, the repetitions of calisthenics, and Taijutsu moves.
Sasuke was also attracted to the idea of using a weapon because that man used a sword and it would not do for Sasuke to be left helpless in case he had to face Kenjutsu. One day, he disappeared from Sakura's house before the two could follow him and returned with a Katana. When Gai saw the Katana, he paired Sasuke off with TenTen.
Sakura had a distaste for being paired with Lee because he was always fawning over her. (Oh, was this how repulsed and uncomfortable Sasuke had felt when she liked him and declared it every moment?) So she tended to pair off with Neji, who didn't have a very nice opinion of her and tried to show her all her faults by beating her into the ground. But Sakura had an obsession now with knowing her weaknesses and trying to learn to compensate for them. She relished the challenge and the first time she was able to use her chakra-control to open a Tenketsu point Neji had shut down, she was almost giddy with achievement at the look on his face when she punched him in the face.
Naruto and Lee had developed a rivalry. Gai approved of the rivalry of the teachers being passed on to their students and told them so. This probably enticed the members of team 7 to cement what would become intense rivalries with the members of team 10 which would last their lives.
Gai was giddy with joy, team 7 was so youthful, just like his Eternal Rival had been. Realizing that they were trying to be like Kakashi endeared them to the Green Beast and he swore to his deceased Eternal Rival that he'd do his best to help team 7 land on their feet and become a team worthy of having had Kakashi as a teacher even if Kakshi was not their teacher any longer.