DENVER --Five of the seven defensive backs who saw work Sunday night were not in uniform when the Indianapolis Colts carved up the Broncos last October.

The newcomers and those with the Broncos who sat out last October did not have the experience that Rahim Moore and Chris Harris Jr. did: to know that the Colts' red-zone offense is among the league's best at keeping a defense off-kilter. The Colts scored 31 of a possible 35 points in the red zone, and Andrew Luck's quarterback rating in that range of the field was 140.9.

"They kicked our butts in the red zone," said Harris.

That wasn't going to happen again. Not with a host of aggressive newcomers. Not with Moore healthy after missing the last nine games of the 2013 regular season and postseason to compartment syndrome.

And no one in the overhauled secondary came up bigger than Moore and Roby. Moore intercepted two passes, including a fourth-quarter grab at the Denver 11-yard-line. Roby made seven tackles, including one at the 1-yard-line, and had the game-saving deflection on the Broncos' final defensive play.

In a 31-24 win, these plays were the difference, and afforded the Broncos just enough breathing room to withstand the Colts' frenzied rally.

"That's what won us the game tonight: making those big plays in the red zone," said Harris.

The biggest was the goal-line stand in the third quarter, and one of the Broncos who came up huge was Roby, who played like anything but the rookie he is, and would cap a night of firsts with a game-saving deflection of a fourth-and-6 pass for Reggie Wayne with 1:51 remaining to clinch the win.

Yes, that's right. In a game between two teams expected to push for the Super Bowl, a rookie was covering a future Hall of Famer for the decisive play. A big deal? It would seem that way, until you consider what Roby faces daily.

"He's covering Demaryius Thomas, Wes Welker and Emmanuel Sanders in practice," said Moore. "So why not?

"I told him I've got him held over top. We're keeping eyes on him. And he's here for a reason. He wasn't a first-rounder just for the heck of it. He made some great plays here, man."

Moore was proud of Roby. So was Harris, who taught Roby all he learned about playing the slot from the last three seasons.

"Everything I see, I'm telling him," Harris said. "He did a great job of catching on, because he didn't know when he was going to play the slot; he just kind of got thrown in, and did a great job at it."

When Harris has started the last two years, he's often moved between the slot and the outside, depending on whether the Broncos were in a sub package or not. Now, he's a full-time right cornerback. That left nickel cornerback duties against the opposing slot receiver to Roby.

"That's tough to do, to play in the slot. That's the role we're looking for him to play, with me playing outside this year, we're looking for him to shut down the inside," said Harris. "I think he did a good job tonight."

Roby's game-saving swat will get the headlines, but was his third-and-goal tackle of Hakeem Nicks a quarter earlier was equally vital. That helped the Broncos maintain breathing room to keep the surging Colts at arm's length.

It was the sort of savvy play you don't expect from a rookie. Nicks lined up outside, and Roby faced him. He cut inside, as the Colts attempted to create space, but Roby did not get caught in traffic, and immediately met him after he caught the pass at the 1-yard-line.

And then Roby held on until help arrived. It came in the form of Quinton Carter, who finished off Nicks.

"Team effort," said Roby.

But the Colts still got to the 1-yard-line. There was no chance for the Broncos to change out of their dime sub package. Normally, fourth-and-goal just one foot from the goal line would belong to the Broncos' short-yardage personnel grouping. This time, the quarterback sneak would be stuffed by linebacker Brandon Marshall and a swarm of defensive backs. Moore, Talib, Harris and Quinton Carter engulfed Luck after Marshall got the initial hit.

"That goal-line stand, man, was one of the best plays I'll never forget," said Moore. "You should have seen our focus and our tenacity, man. Just flying around. It was great to see.

"It just shows that we've got guts, man," Moore added. "When it was time for us to stand up, we did."

Eleven months ago, the Broncos merely saw red. Sunday night, it meant stop. And while the re-shuffled secondary will pick apart its shortcomings, it can lean on the fact that it delivered when it was needed most.