What does Pony mean on page 123 of The Outsiders when he says, "We could get along without anyone but Johnny"?

Johnny Cade is the smallest member of the greaser gang
and, next to Ponyboy, the youngest. He has the worst home life of them all: His parents
argue all the time, and his father beats him. He has previously been attacked and badly
beaten by a gang of Socs, so he now rarely travels alone and has taken to carrying a
knife. He is sensitive, like Ponyboy, and somewhat withdrawn. He is akin to a team
mascot--the favorite of all the boys, especially Dally, who has few close friends.
Although part of the boys' concern for Johnny comes from a sympathetic nature, Johnny is
the unifying force between many of them. The gang needs Johnny as much as Johnny needs
them.