"Cool," he said.
Then the Carolina Panthers coach reminded he would be preparing for the Ravens next, explaining why he didn't elaborate. Reminded he would be asked about the Ravens' No. 1-ranked defense this week as well, Rivera said his answer would be the same thing, "Cool."
Rivera knows about cool defenses. He played on arguably the coolest one in NFL history in 1985 when the Chicago Bears led the league in seven defensive categories on their way to winning Super Bowl XX.
That unit even had a cool nickname, "Monsters of the Midway."
The Panthers (4-2) haven't come close to that level. They're not even playing at the level of the Ravens (4-3) heading into Sunday's 1 p.m. ET game against Baltimore at Bank of America Stadium.
But if the last quarter and a half of Sunday's 21-17 come-from-behind win at Philadelphia is an indication of what the Carolina defense can do, it is headed in the right direction.
Quarterback Cam Newton and the offense got most of the credit for overcoming the 17-0 deficit in the final 11 minutes. But that wouldn't have happened had the defense not completely stymied Carson Wentz & Co.
The Eagles had 120 yards total offense in the second half after registering 222 in the first, and most of that came on the first series of the third quarter when Wentz passed for 73 yards and a touchdown to make it 17-0.
In the fourth quarter, the Eagles were limited to 25 total yards.
Even then the defense had to, in the words of Rivera, "win the game twice" because officials overruled an interception by safety Eric Reid with 1 minute, 11 seconds remaining and Philadelphia at the Carolina 22.
Future Hall of Fame defensive end Julius Peppers took care of the second time, collecting his second strip-sack in as many games to stop Wentz on fourth down at the 14.
"It gives you a foundation and a perspective to grow and build on," defensive coordinator Eric Washington said of the second-half effort. "We know what we're capable of doing."
That the Panthers haven't gotten off to the fast start Baltimore has defensively shouldn't come as a surprise. In three of the five seasons Rivera's defense has ranked among the top 10 in the league since 2012, that unit has played much better in the final 10 games than in the first six.
The 2014 season is perhaps the best example. Carolina ranked 26th in total defense after six games, then had the fourth-best unit over the next 10 games to finish the regular season ranked 10th.
Rivera cites not having the same secondary to start consecutive seasons as a big reason. This year's unit is no exception. The Panthers opened with a rookie cornerback in Donte Jackson and new free safety in Da'Norris Searcy.
When Searcy was placed on injured reserve after three games, Reid was brought into the mix.
"We've been in flux in the secondary," Rivera said. "So a lot of it has to do with eventually you come together and adjust. Sometimes we've gelled faster. I think we're pretty much on track."
Sunday's game will give the Panthers, ranked 13th defensively, an idea of where they stack up since the Ravens have been the measuring stick so far this season.
"We can be special," nickelback Captain Munnerlyn said. "We've just got to find a way to play a complete game."
The pieces are there. Luke Kuechly, who had 14 tackles (four for loss) and a sack against the Eagles, is arguably the best middle linebacker today. With Thomas Davis back from a four-game suspension, and with Shaq Thompson playing at a high level, the outside linebackers are among the league's best.
Kawann Short, who had two tackles for loss against the Eagles, is third among defensive tackles in sacks with 26.5 since 2015. Defensive end Mario Addison ranks fourth in the league with 23.5 sacks since Nov. 6, 2016.
Peppers is starting to get into a rhythm after sitting most of the offseason and training camp. With a sack in consecutive games, he's only four from surpassing Kevin Greene (160) for third place on the NFL's all-time list.
This front seven held Philadelphia to a season-low 58 yards rushing,
The secondary has been solidified by Reid, who had eight tackles and appeared to have the game-saving interception before what he called a "terrible" reversal by the officials.
And remember, Washington is Carolina's third defensive coordinator in three years with Sean McDermott (Buffalo) and Steve Wilks (Arizona) moving on to head-coaching jobs the past couple of years.
With every game, Washington gets more comfortable calling plays and making halftime adjustments. The decision to become more aggressive in the second half with pressure on Wentz was as big as Newton's two touchdown passes.
"I have to improve just like the players do," Washington said.
The Carolina defense hasn't made the big splash that the Ravens did with a franchise-record 11 sacks against the Titans. But few in league history have, given that the NFL single-game record is 12 (held by four teams).
"That's rare," Davis said of Baltimore's 11 sacks. "That's kind of what I see this front seven is capable of doing. On any given Sunday we can produce those kind of numbers.
"It's not about one person, not about two people. It's about the complete group going out and doing their job."
That goes back to Rivera's theory that it takes time for a new secondary to gel with the front seven. The second half against Philadelphia could be a sign things are coming together.
"It gives you some things to reference and build on as we move forward," Washington said. "Our season is a work in progress. It's about growth and maturation of a team, of a defense or individual players.
"I like the direction we're going in."