Will Hill had to learn to rely on himself before his teammates could rely on him. To accomplish that goal, those teammates had to let Hill know how much he was needed.

That’s the lesson learned this season by the Giants’ up-and-coming safety. It could prove to be the most valuable lesson of his career.

Hill has the athleticism and ability to be a game-changer, and now he is in the proper place on the field — and in his life — following a suspension his rookie season and another for the first four games this season.

“We had to let Will know how much we need him on this team, and show him that we had trust in him,’’ veteran safety and team leader Antrel Rolle told The Post Friday as the Giants prepared for Sunday’s clash against the Chargers in San Diego.

“We let him know how much of a necessity he is to this team. Once he understood that he is needed and is wanted, it helps him as far as his transformation outside of football. You can’t let us down. He understands that exactly now.’’

Powerful words have created a powerful change in Hill.

“To miss those games and be able to come back and help the team in the way I’ve been helping them has been awesome,” Hill said, “because the organization and my teammates still believe in me, and that has helped me overcome so many thing.

Hill was hit with a four-game suspension to open the season for violating the NFL’s substance abuse policy after he admitted to smoking marijuana. A star at Jersey City’s St. Peter’s Prep, Hill said he will keep his act clean.