Ben McAdoo suffered his first loss on the day he was introduced as the Giants’ new head coach.

McAdoo targeted Joe Philbin to be his quarterbacks coach — possibly also carrying the designation of assistant head coach — but Philbin was hired as the Colts’ offensive line coach on Friday. No wonder McAdoo called assembling his staff “very fluid at this point.’’

McAdoo and Philbin — the former Dolphins head coach — worked together with the Packers and he would have been an experienced right-hand man for McAdoo to lean on.

“Joe Philbin I think the world of,’’ McAdoo said. “I think he’s a talented man, talented coach, one of the best I’ve been around, think the world of him.’’

But McAdoo will have to appreciate Philbin from afar.