They have become great friends, and so there was symmetry when the suspension of Dominique Rodgers-Cromartie opened the door for cornerback Donte Deayon to make his NFL debut last week in Denver.

When Rodgers-Cromartie was dropped from the Giants’ roster last week, Deayon was signed off the practice squad to take his place and ended up playing 39 of the 81 defensive snaps in the 23-10 victory over the Broncos.

“Man, it was like a father watching his son,” Rodgers-Cromartie said. “For him to go out there, he’s energetic just like me, he brings a lot of fun to the game. Best thing I told him was don’t let up, stay out there, regardless of what happens with me, stay out there, keep going, keep doing what you’re doing.’’

Deayon, 23, laughed when he was told Rodgers-Cromartie, 31, thought of him like a son.

“He’s funny,’’ Deayon told The Post. “That’s my big bro. Definitely not my dad. Not a chance.’’

With Rodgers-Cromartie activated after missing one game, Deayon could have been put back on the practice squad, but he stayed on the roster after a promising first game.

“Donte provides a lot of energy for the whole team,” coach Ben McAdoo said. “He loves football. He gets football and he had a nice start to his NFL career the other night.”

On his first NFL play, Deayon made the tackle on kickoff coverage. In the third quarter, he put a big hit on Emmanuel Sanders, forcing a dropped pass. Because Deayon is generously listed at 5-foot-9 and 163 pounds, putting a big hit on anyone is impressive.

“Obviously, when you’re evaluating players there is a certain height, weight and speed that you’re looking for,’’ McAdoo said. “It’s no secret he doesn’t fit into that. He carries that with him as a chip on his shoulder. He’s not afraid to mention to me that he feels like he’s getting taller as the season goes on. But he’s an impactful young man.”

Deayon, a teammate of safety Darian Thompson’s at Boise State, does not walk inside the locker room. He bounces. He is not always smiling, but close. Whenever his name is mentioned, defensive coordinator Steve Spagnuolo lights up.

“Love that guy,’’ Spagnuolo said. “We have to keep oiling him up, keep getting him reps.’’

This could have been a one-and-done for Deayon, filling in for Rodgers-Cromartie. Instead, he will play alongside him at times Sunday against the Seahawks.

“I got an opportunity so I knew I had to play well,’’ Deayon said. “When [Rodgers-Cromartie] came back and I could have gone back down, I would have had that gauge that I know I can play in this league. It felt good.’’