Carson Palmer's value to the Arizona Cardinals became undeniably evident last season. It's been equally transparent through the first two weeks of this one.

Palmer vies for a ninth consecutive victory under center and the Cardinals aim for a second straight 3-0 start when they open NFC West play Sunday against the visiting San Francisco 49ers.

Arizona (2-0) was firmly in the driver's seat for the NFC's No. 1 seed last season until Palmer tore his left ACL in a Week 10 win. The Cardinals dropped four of six after their 9-1 start and finished a game behind Seattle in the NFC West.

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Palmer has displayed no rust from the layoff. After throwing for three touchdowns in a 31-19 victory over New Orleans, he had four more in last week's 48-23 road rout of Chicago.

The 35-year-old has produced 492 yards and a 124.4 passer rating over the two wins. More importantly, Palmer is 15-2 over his last 17 starts and hasn't lost since a 23-20 defeat to the 49ers at University of Phoenix Stadium in the 2013 finale. It's the longest active streak among NFL quarterbacks and longest by a Cardinal since Ray Mallouf won 10 straight in 1948.

"Right now he's playing at a championship level," said Cardinals tight end Jermaine Gresham, also a teammate of Palmer in Cincinnati in 2010. "He's always had it, but he's surrounded with so many guys here right now. He's just clicking right now. He's zoned in."

A rejuvenated Larry Fitzgerald and big plays on defense and special teams have also contributed to Arizona's latest strong start. Fitzgerald broke out for eight catches, 112 yards and three touchdowns - one more than his 2014 total - against Chicago, and the Cardinals also received a pivotal interception return touchdown from Tony Jefferson late in the first half and a team-record 108-yard kick return score from impressive rookie David Johnson on the opening kickoff.

"I've never been around this deep of a team," Fitzgerald said. "I was around Hall of Famers in Anquan (Boldin) and Edgerrin James and Kurt Warner, but besides that, on the offensive side of the ball I've got some guys that really can play over there."

Johnson, a third-round pick from Northern Iowa, has certainly made the most of his opportunities. He had a 55-yard touchdown reception on his first NFL touch against New Orleans and rushed for 42 yards and a touchdown on five carries last week. Coach Bruce Arians told reporters that Johnson should have a larger role this week behind Chris Johnson, who had 72 yards on 20 carries against the Bears starting in place of the injured Andre Ellington.

Ellington will miss a second straight game with a sprained knee, but guard Mike Iupati and right tackle Bobby Massie are expected back to an offensive line that's yet to allow a sack.

Iupati, who made three Pro Bowls in five seasons with San Francisco (1-1) before signing with the Cardinals in March, missed the first two weeks with a knee injury and Massie completed a two-game suspension for a substance abuse violation.

Iupati was one of several high-profile offseason defections for a retooling 49ers team that's delivered mixed results to begin the post-Jim Harbaugh era, particularly on defense. After recording five sacks and limiting Minnesota to 248 yards in a 20-3 home win in Week 1, San Francisco surrendered 453 while yielding a slew of big passing plays in a 43-18 loss at Pittsburgh last week.

The Steelers averaged 8.7 yards per play, with Ben Roethlisberger amassing 369 yards and three touchdowns while completing 21 of 27 passes.

"They just flat out beat us. We took it in the chin," 49ers defensive lineman Glenn Dorsey said. "We put ourselves in a lot of bad situations uncharacteristic of our defense."

San Francisco also played most of the second half without Carlos Hyde after the second-year running back suffered a leg contusion and took a shot to the head. Coach Jim Tomsula said afterward that Hyde's departure was precautionary and he passed concussion tests.

Hyde rushed for a career-high 168 yards and two touchdowns against Minnesota but was held to 43 on 13 carries last week.

Colin Kaepernick did throw for 335 yards and two TDs in the loss and owns a 9-to-1 touchdown-to-interception ratio while winning four of five starts against Arizona. The lone defeat occurred in Glendale during Week 3 of last season, with Drew Stanton throwing two second-half TD passes to John Brown to rally the Cardinals to a 23-14 decision while starting in place of Palmer.

San Francisco has won 10 of 12 in the series, but has split its last four visits to Arizona.