The pick-six was nice, something he'll always remember, but Miles Killebrew's most important play came much earlier in Sunday's season-opening win over the Arizona Cardinals.

Late in a lackluster first quarter, with the Cardinals threatening to take a two-touchdown lead, Killebrew made a red-zone tackle on a screen pass to Jermaine Gresham that he might not have been in position to last year.

The Cardinals had just gotten a fresh set of downs after a Lions penalty, and on third-and-goal from the 2-yard line, they tried to take advantage of the Lions' aggressive defense.

Gresham motioned to the right side of the formation and at the snap latched on to defensive end Cornelius Washington as if he was pass blocking for quarterback Carson Palmer. With four of his teammates running pass routes towards the end zone, Gresham tossed Washington to the ground and released for what the Cardinals hoped would be an easy score.

Killebrew, playing as an extra safety in the Lions' big nickel package, kept his eyes trained on the backfield and triggered in Gresham's direction when the big tight end released from the formation.

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Before right tackle Jared Veldheer could kick outside for the block Gresham needed to reach the end zone, Killebrew shot the gap and grabbed hold of Gresham's leg for a touchdown-saving tackle.

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For the second-year Lions' safety, that play was part of a banner season-opener in which he finished with three tackles (including one on special teams), defended two passes and made good on his off-season focus to show better awareness on the field.

"I really wanted to focus on my eyes," Killebrew said after the Lions' 35-23 victory. "As a young player, I noticed my eyes were kind of all over the place sometimes, which is probably to be expected. But that’s something I really wanted to focus on and hopefully moving forward I can continue to get better."

Just 17 games into his NFL career, Killebrew looks like an important part of the Lions' defense, now and into the future.

Last year, he played as a dime defender and was one of the Lions' most efficient players on a per-snap basis. He made 28 tackles and had one interception while averaging less than 10 snaps a game.

On Sunday, Killebrew played as the third safety and shined in a career-high 29 snaps.

"I think everybody noticed from the first time that he was in a ball game that he was around the ball a lot," Lions coach Jim Caldwell said. "He’s active, he runs, and he runs hard all the time. I think that without question helps him get himself in a position where he’s always around the ball."

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Killebrew, known as a punishing hitter and top run defender coming out of Southern Utah last year, was especially effective as a pass defender Sunday.

In the third-quarter, he batted down a pass to tight end Troy Niklas on a seam route down the field.

The Cardinals scored two plays later to take a 17-9 lead on a rushing play to Killebrew's side of the field, but when it came time to seal the game at the end, Killebrew hauled in a deflected pass off Andre Ellington's arm and returned it 35 yards for a touchdown.

"I saw it bounce up in the air, my eyes got about this big and next thing I know I’m in the end zone," Killebrew said.

Killebrew held tightly onto the ball as he returned to the sideline to celebrate after his touchdown, and Caldwell said Monday that play — and his performance Sunday in general — helps show how much Killebrew has developed.

"His progress has been good because he’s got the right traits," Caldwell said. "He works at it. He loves it. He has great passion. And he has the talent level."

Contact Dave Birkett: dbirkett@freepress.com. Follow him on Twitter @davebirkett. Download our Lions Xtra app for free on Apple and Android!