Rivers, who played all three of his previous seasons with the Cincinnati Bengals, missed last year with a wrist injury. He thought he would be more nervous than he was Friday.
"It was good to get back into the swing of things and be amongst the land of the football living," said Rivers, who finished the game with two solo tackles.
The Giants traded a fifth-round pick in the offseason to acquire Rivers from the Bengals in hopes that he can stay healthy and show the skills that made him the ninth overall pick in 2008.
Rivers said it's a big year for him coming off the injury and he is ready to grab any opportunity -- like starting Friday -- that comes his way.
"You got to minimize mistakes and capitalize on the opportunities you have to make plays," Rivers said. "Just got to be consistent really know what your assignment is."
Rivers wants to earn a full-time starting role but understands he's playing with the defending Super Bowl champions.
"So it's not like you're coming to some team that doesn't have players," he said. "These guys can play and I'll just keep plugging away, keep my head to the grindstone."
During a conference call Saturday, head coach Tom Coughlin said Rivers "showed us his quickness, his abilities, his athleticism, his ability to be physical."