In the Naruto Wiki it states:
"Sakura's exceptional intelligence and keen observation skills also improved during her training with Tsunade, who taught her to read and decipher the attack patterns of her enemies and act accordingly. As a result, she could now read complex patterns in her opponent's attacks, even opponents as strong as Sasori, a feat which even surprised an experienced war veteran like Chiyo."
"When Sakura along with her team encountered Tobi and his technique, Sakura was able to assume its mechanism and deduce that Tobi was only pretending to be affected."
"Sakura was able to work out that the spy wasn't using the Transformation Technique as the sensors would've detected the spy. When having a talk with "Neji", Sakura was able to deceive him and attack him while he was unprepared. She was able to extract information from the assassin and piece together the mechanics behind the enemy's abilities, using information she had come across previously, as well as what the clone told her."
Useless? Nope! Just currently not involved in this part of the story, but the manga's not over yet.