I believe using summons without chakra seal is possible. Her giant strength is surely usable even without the seal, so why not summons?
It's even called differently, White Strength Seal, instead of Yin Seal. But that, again, is beside the point.
She should've stopped accumulating chakra and used it for saving Naruto.
I once again repeat, Naruto captured = GAME OVER MAN, GAME OVER!
Thank the powers that be that Hinata isn't such a pussy.
You DO know that Kishi's decision, right? It's not that Sakura didn't want to save Naruto, it's that she didn't know he needed help.
Hinata didn't as much as 'save' Naruto as much as being slapped in half a page. In that point, Kishi only needed someone to enrage Naruto into going Kyuubi, and at that moment, Hinata was it. Before, it was OROCHIMARU.
Seals are simply an aid for performing jutsu, the manga has shown that much. People with sufficient skill can mold chakra without seals. If I recall the second hokage was able to use several of his water jutsu without using seals at all.
Hinata knew naruto was in trouble because she had a byakugan, sakura is not so lucky in that department. Its not like sakura was just watching hinata trying to save naruto, she was simply elsewhere. And stop saving chakra for what? The manga has hinted plenty that her seal was unusable until it was fully charged. Even if sakura had gone to save naruto during the pain invasion the power would have likely been unavailable to her. If that power was actually available to her earlier then there would have been plenty of situations where she would have used it such as to save her ass when fighting sasori.
Are you guys being intentionally dense?
Step Zero. Ask the byakugan guy that was with Sakura about Naruto's condition. He says Naruto's in a world of shit. Then comes...
Step One. Stop accumulating chakra for the seal. Forget the seal! Use the already accumulated chakra for something else entirely! Assist Hinata, for example!
Step Two. Get Naruto out of combat!
That would be all.
Maybe Kishi had this idea of making Naruto,Sasuke & Sakura Konohas next legendary 3 Sannin, even before he mentioned them in the Manga.This picture shows them with the summons posing. It's from 2000 and since then, I'm waiting for this scene to appear in the storyline.
The thing is, Kishi allways keeps his old character scetches in mind to use them somehow.
Just look into the first Naruto Databook,you'll notice that he showed Jiraiya in his frog-transformation with the elders on the shoulders,
hundreds of chapters before,for example.
I think he'll probably show us some training panels or a whole chapter of Sakuras training,thats all.
Kishi missed to mention Sakura for a long time and now its a little bit too late to show her so powerfull all of a sudden.
She should've had some solo-chapters in the past showing her improving.Just giving us a backflash would be boring.
Maybe Naruto/Kurumas chakra gave Sakura the last bit she needed to reach 100% of charging. All other Shinobi got really strong,too,after/while receiving their chakra.That would be kind of an explanation for her, being able to use this new jutsus.On the other hand she always wanted to be equal to Naruto & Sasuke,therefore she had to endure every "Pain" for 3 whole years,even not being able to fight with full power or help Naruto like Hinata did.Just to be handy when Team 7 reunites,even if it's for a small period of time.(Don't know how long she can fight with the mark.)
And we do not know when Sakura made her contract with Katsuyu,eventually it was just before the war began,so she couldn't summon her at all before the war.
I don't really need an explanation for her powers anymore,since Kishi left Sakura more/or less out of the story after the Sasori fight.
He wasted this character and now as the story needs her,'cause she's one of the 3 main characters, he remembers Sakura,but it's too late for that.
Even if she can do the summon & the seal,in the end she's nothing,compared to Naruto & Sasuke.Sad,cause i liked this character.
Hopefully Kishi will give her more space as an acting-,not background-figure in the future.