This quotation describes Flick, the former high-school basketball player, working as an attendant at a gas station. Updike personifies the "idiot" gas pumps to suggest how they appear to Flick. Flick perhaps feels that this job is not where he wanted to end up, and so his perception of the pumps as idiots is an indication of his frustration. He feels that this job is beneath him.
Updike continues to personify the pumps as basketball players. There are even "Five on a side," just as there would be five players on each side in a basketball game. The pumps also have "rubber elbows hanging loose and low," which perhaps alludes to the defensive stance of a basketball player. The implication is that Flick can't escape the glory days of his past as a high-school basketball player. He imagines the pumps as fellow players and himself "stand(ing) tall" among them, just as he might have stood above or been better than his fellow players at school. He is likely always reliving in his imagination those glorious high-school days, so much so that he still projects them onto the present. This is Flick's way of hanging onto the past, and, at the same time, denying the disappointment of his present.