Naruto could use his Uzumaki bloodline's chakra reserves. He might overwhelm Might Guy with a large number of shadow clones, confusing him and creating an opening to save Tenten.
It could be that Might Guy is under some sort of mind - control. So, without his normal self - control, he attacks Tenten, making it necessary for Naruto to save her.
Well, perhaps in this fanfiction, Might Guy is possessed by some sort of dark force. This makes him turn on Tenten during a sparring session. Naruto, being the hero he is, arrives just in time. He first tries to talk to Guy, but when that fails, he uses his speed and agility, skills he's honed over years of fighting. He quickly grabs Tenten and gets her to safety, then he has to figure out how to free Guy from the dark influence.
Naruto could use his shadow clone jutsu to create distractions. While Gai is busy dealing with the clones, Naruto can quickly get Tenten to a safe place.
Perhaps in the fanfiction, there's a misunderstanding. Guy Sensei thinks Tenten has stolen a valuable jutsu scroll or something important to him. Naruto, knowing Tenten is innocent, stands in front of her. He might try to reason with Guy Sensei first, using his charm and quick - thinking. If that doesn't work, he'll be ready to fight, using his Rasengan if necessary.
Maybe there was a misunderstanding. Might Guy could have thought Tenten was involved in something bad, like stealing a valuable scroll from the village that he was trying to retrieve.
Well, Naruto has his Nine - Tails chakra. He could potentially tap into that power to either overpower Might Guy or create some kind of shield around Tenten. He might also use his Rasengan, but in a non - lethal way to stop Might Guy's attacks long enough to protect Tenten. Also, Naruto is known for his quick thinking and adaptability in battle, so he could come up with a unique strategy on the spot depending on the situation.
His relationships would also develop. By protecting Tenten, he would earn her trust and respect. This could lead to a stronger bond between them and also with other members of their ninja group. Naruto might also gain a new perspective on Guy Sensei, understanding that even strong and respected teachers can be vulnerable to certain influences. He would learn to look beyond the surface and be more empathetic towards others.