I already said this but Benny was DEFINITELY friends with Phillips. They had to be. I think they played on the same baseball team and they were best friends for many years. But then baseball started getting less fun because the coach and the rest of the players only cared about winning. Benny didn't like that so he left.
Phillips is mean to Benny and the sandlot boys because he's never forgiven Benny for leaving him with a shitty team.
Night Benny left the team
"Come on Benny don't do this man!" Phillips pleaded "I need you! I can't play alone with these guys!"
"Sorry man but baseball shouldn't be just about winning,I'm not happy here anymore"
"So that's it? You're just gunna leave?"
"We can still be friends Phillips-"
"No!" Phillips cut him off "I don't wanna be your friend anymore!"
That really hurt Benny because he lost his best friend. That's why Benny is kinda serious because he's scared to open up and loose his sandlot friends like he did Phillips.