The Cardinals' defense was a sieve in 2019 and not much changed through the first two possessions of 2020.
The 49ers scored a field goal on their opening drive Sunday and then Raheem Mostert beat rookie linebacker Isaiah Simmons for a 76-yard touchdown on the first play of their second series.
But this is a new year, and possibly, a new defense.
San Francisco struggled to move the ball from that point forward, accumulating only 10 points and 4.7 yards per play after the initial burst. The Cardinals allowed 20 points in the contest, a lower total than all but one game in 2019.
"They battled their tails off the rest of the game," coach Kliff Kingsbury said of the defense. "It was hot. That's a very good offense and a great playcaller. We had a couple tough breaks early but competed. It seemed like every throw, every run was contested, so really impressed by the coaching staff and their adjustments, and the players' overall effort, that kind of refuse-to-lose mentality with some of those stops they had there at the end."
The Cardinals finished last in total defense and 28th in points allowed a season ago but General Manager Steve Keim went to work fortifying the group this offseason.
Free agent additions Devon Kennard and De'Vondre Campbell combined for one of the most crucial plays of the contest, stuffing Mostert on fourth-and-goal from the 1 in the second quarter. Angelo Blackson, who was signed just last week, had the team's first sack.
"I do think Steve has done a great job of bringing in quality talent that has fit in really well," Kingsbury said. "It gives us a chance to rotate more guys in, and they're going to need it. You saw it yesterday. (Safety Jalen Thompson) got hurt the second play of the game and Chris (Banjo) was able to step in and play at a high level the remainder of the game."
While the first game was a noticeable departure from last year's struggles, there are reasons for caution.
San Francisco was without its two best receivers – Deebo Samuel and Brandon Aiyuk – due to injury, and tight end George Kittle was a non-factor after absorbing a big hit from safety Budda Baker late in the first half.
Additionally, Simmons, the No. 8 overall pick who is expected to have a big impact, struggled in his debut, giving up the Mostert touchdown and then possibly getting mixed up in coverage on Jerick McKinnon's fourth quarter score.
"Isaiah was in his first game, obviously, and it was moving pretty fast for him to start," Kingsbury said. "I thought he settled in as the game went on, but there's going to be some growing pains early on in the season. … He's a tremendous talent and I expect him to get better and better as the weeks go on."
It was not a perfect outing, but there seems to be a blueprint for success. Baker, outside linebacker Chandler Jones and cornerback Patrick Peterson had solid games, and unlike last year, they had plenty of help.
Baker believes the defense should continue to ascend as the season progresses.
"This is the first time we did real live contact, tackling guys, and now it's just a matter of building," Baker said.
The Cardinals relied on Kingsbury and quarterback Kyler Murray too much last season, as the defense had a tough time coming up with critical stops. Sunday was different, as Murphy's back-to-back pass breakups as time winded down sealed a game-winning stand.
Even though Murray and wideout DeAndre Hopkins were the toast of the team following the game, the balance shown in the win will be critical as the season moves forward.
"Both phases and special teams, especially, kind of rose up together when we needed it the most yesterday, and made plays," Kingsbury said. "And that's what you're looking for."
Images from the season opener in Santa Clara