@Adamant:
This is a special one-shot done as part of a series made by popular writers, not something intended as a pilot for a series. There's not going to be a serialized version.
And even if it WAS intended as a pilot, the girls could've easily been added to the serialized story once that got started. They served no purpose in THIS story, so why have them there?
They served no purpose because there wasn't a purpose to serve in the first place. You don't waste space in a one shot going into detail about every little character. We saw the backstory and character quirks of the two main guys, because that's all you need to see in order to keep the story moving. The girls? The pitcher? The bad guys? They're just there to put the main characters into situations where they can interact with the world around them, so the reader may learn about it while simultaneously being fed characterization, and in that respect that fulfilled their role just fine. This is how pretty much any One-shot or first chapter of a manga works, or indeed almost any work of fiction.
And you honestly think this doesn't also serve as a pitch to SJ by Kishimoto? Naruto looks to be nearing an end, and he's not about to just stop the gravy train he's managed to set up for him.
Who, the D-team catcher? They needed a catcher for the story. Of course he could've been made more interesting, but at least he had a purpose to fill. The girls were just talking background objects, with one of them supplying a tiiiiny bit of exposition which could've been given by the catcher anyway.
And they don't need a manager character in a baseball story?