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.
Between the talent infusion and the improvement made by second-year players like cornerback Byron Murphy Jr. and defensive end Zach Allen, the defense looked deeper than at any point last year.
"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
Cardinals RB Chase Edmonds dives for a touchdown.
49ers quarterback Jimmy Garoppolo (10) passes against the Cardinals during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
WR DeAndre Hopkins
QB Kyler Murray
Cardinals RB Chase Edmonds (29) dives past 49ers linebacker Kwon Alexander (56) to score a touchdown.
LB De'Vondre Campbell (59) and LB Devon Kennard combine for a goal-line stand.
49ers running back Raheem Mostert (31) runs toward the end zone to score a touchdown against the Cardinals.
Arizona Cardinals quarterback Kyler Murray (1) passes against the San Francisco 49ers during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Cardinals coach Kliff Kingsbury watches from the sideline.
WR Larry Fitzgerald
San Francisco 49ers players and coaches stand in the far end zone during a presentation on social justice at Levi's Stadium before an NFL football game between the 49ers and the Arizona Cardinals in Santa Clara, Calif., Sunday, Sept. 13, 2020.
San Francisco 49ers running back Raheem Mostert (31) runs against the Arizona Cardinals during the second half of an NFL football game in Santa Clara, Calif.
Cardinals cornerback Byron Murphy Jr. (33) breaks up a pass intended for San Francisco 49ers wide receiver Trent Taylor during the second half.
Arizona Cardinals wide receiver DeAndre Hopkins (10) runs against the San Francisco 49ers.
San Francisco 49ers fullback Kyle Juszczyk (44) catches a pass against Arizona Cardinals outside linebacker Haason Reddick (43) during the second half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Cardinals quarterback Kyler Murray (1) scrambles from San Francisco 49ers defensive end Nick Bosa during the first half.
Arizona Cardinals head coach Kliff Kingsbury, right, watches during the second half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals wide receiver Larry Fitzgerald (11) reacts during the first half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif.
Arizona Cardinals wide receiver DeAndre Hopkins (10) catches a pass against San Francisco 49ers cornerback Emmanuel Moseley.
Arizona Cardinals running back Kenyan Drake (41) is congratulated by teammates after scoring against the San Francisco 49ers.
San Francisco 49ers defensive end Kerry Hyder Jr. (92) pulls down Arizona Cardinals quarterback Kyler Murray.
San Francisco 49ers running back Jerick McKinnon (28) runs against Arizona Cardinals middle linebacker Jordan Hicks (58) and outside linebacker De'Vondre Campbell.
Arizona Cardinals quarterback Kyler Murray (1) passes against the San Francisco 49ers during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals running back Kenyan Drake (41) runs past San Francisco 49ers middle linebacker Fred Warner (54) during the first half of an NFL football game in Santa Clara, Calif.
Arizona Cardinals wide receiver DeAndre Hopkins (10) catches a pass against San Francisco 49ers cornerback Emmanuel Moseley (41) during the first half.
San Francisco 49ers tight end George Kittle (85) runs against Arizona Cardinals strong safety Budda Baker during the first half.
Cutouts are seated at Levi's Stadium as Arizona Cardinals kicker Zane Gonzalez (5) kicks a point after try during the first half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Cardinals quarterback Kyler Murray (1) runs past San Francisco 49ers cornerback Richard Sherman to score a touchdown during the second half.
San Francisco 49ers tight end Jordan Reed (81) runs against Arizona Cardinals outside linebacker De'Vondre Campbell during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals quarterback Kyler Murray (1) runs past San Francisco 49ers cornerback Richard Sherman (25) to score a touchdown during the second half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals linebacker Chandler Jones (55) sacks San Francisco 49ers quarterback Jimmy Garoppolo during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals defensive tackle Rashard Lawrence (92) celebrates during the first half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif., Sunday, Sept. 13, 2020.
San Francisco 49ers quarterback Jimmy Garoppolo (10) passes against the Arizona Cardinals during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals quarterback Kyler Murray passes against the San Francisco 49ers during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals cornerback Patrick Peterson (21) gestures during the second half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif., Sunday, Sept. 13, 2020.
San Francisco 49ers running back Raheem Mostert (31) runs toward the end zone to score a touchdown against the Arizona Cardinals during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
San Francisco 49ers running back Jerick McKinnon, left, runs against the Arizona Cardinals during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals quarterback Kyler Murray (1) passes against the San Francisco 49ers during the first half of an NFL football game in Santa Clara, Calif., Sunday, Sept. 13, 2020.
Arizona Cardinals wide receiver Larry Fitzgerald (11) celebrates during the second half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif., Sunday, Sept. 13, 2020.
San Francisco 49ers head coach Kyle Shanahan and Arizona Cardinals head coach Kliff Kingsbury shake hands after an NFL football game on Sunday, Sept. 13, 2020, in Santa Clara, Calif. The Cardinals won 24-20.
Arizona Cardinals wide receiver DeAndre Hopkins (10) celebrates with cornerback Patrick Peterson (21) during the second half of an NFL football game against the San Francisco 49ers in Santa Clara, Calif., Sunday, Sept. 13, 2020. The Cardinals won 24-20.
