GLENDALE, Ariz. — Ron Rivera called for the big-game uniforms again. Waiting in each of the visitor’s lockers at State Farm Stadium were freshly washed white jerseys with burgundy numbers, draped over shoulder pads and sitting atop white pants.

His players got the message.

Six days after wearing their white-on-white uniforms to upset the Pittsburgh Steelers, the Washington Football Team played big again, this time in a critical conference matchup on the road.

With its defense leading the way, Washington defeated the San Francisco 49ers, 23-15, in Arizona on Sunday to extend its winning streak to four games and improve to 6-7. The defensive-led victory inched Washington closer to a once-improbable playoff berth, thanks in part to the Arizona Cardinals’ win over the New York Giants earlier in the day.

It also added to the lore of Washington’s inspired turnaround after years of losing and disappointment. The team changed quarterbacks a third time this season when Alex Smith, five games into his remarkable comeback, was sidelined because of calf soreness in his surgically repaired right leg. Dwayne Haskins took over in the second half, but the star of the game was Washington’s talented defense, which more than made up for the offense’s sluggish performance, scoring 17 points off three takeaways to move the team into first place in the NFC East.

“They bowed their necks when they had to,” Rivera said of his defense. “ … Those guys rose to the occasion.”

If Washington’s win in Pittsburgh was one for the ages, its win in Arizona was a win for the defense — and a sign that this team, led by its strongest unit, is a viable playoff contender.

But, of course, the win had to include a bit of drama.

Smith appeared off from the beginning, with passes that were underthrown or wildly off target and a general inefficiency that permeated the offense for much of the first half. San Francisco jumped to a 7-0 lead on a seven-play drive that culminated with a one-yard rushing touchdown and amassed 96 yards in the first quarter. Smith could muster only five passing yards in that span.

Failures on early downs resulted in many third and longs that Washington couldn’t convert — not without its tackle-breaking rusher, Antonio Gibson (turf toe), or with its starting quarterback at less than 100 percent.

Rivera said afterward that Smith — who finished 8 for 19 for 57 passing yards, an interception and a 27.7 rating — experienced tightness and soreness in his right calf in between series in the second quarter. He was surrounded by team doctor Robin West and trainers as he sat on the bench with a heating pad wrapped around his leg. Although X-rays taken during halftime were negative, Smith couldn’t get loose, so Rivera called for Haskins. Smith, designated the emergency quarterback, watched the second half from the sideline while holding his helmet to his ear to listen to the play-calls.

By then, Washington’s top playmakers were all nicked, if not worse. Wide receiver Terry McLaurin, who hasn’t missed a game but has been on the injury report with an ankle issue since Week 12, was hobbling after a catch and had his left ankle taped before he returned to the game in the first quarter.

The wounded list only grew from there. Free safety Deshazor Everett was sidelined with a chest injury, linebacker Kevin Pierre-Louis left with an ankle injury, and defensive tackle Jonathan Allen went out in the fourth quarter with a groin injury.

Despite it all — the quarterback change, the injuries, the lack of offensive production — Washington found a way. Turns out, it didn’t really need its offense to produce. The defense, led by rookie pass rusher Chase Young, could do it all.

Young has been on a tear since the team’s Week 11 win against the Cincinnati Bengals, and in Arizona, his play reached a record level. He smothered Nick Mullens for a sack after first dropping back in coverage and then closing quickly on Mullens after reading the 49ers’ play. He forced a fumble in the second quarter that set up Washington’s first score, a 31-yard field goal. A few minutes later, he recovered a fumble forced by Daron Payne and ran it back 47 yards for a touchdown.

In between, he had two batted passes, becoming the first rookie in NFL history (or at least since 1999, when the stats were first recorded), to achieve all of that in a single game.

“When I picked it up, I was like: ‘I can’t go down. I got to score,'” Young said, recounting his fumble recovery. “ … I’m just glad my teammates were there running down the sideline with me because they definitely helped me get there.”

To close out the third quarter, rookie safety Kam Curl intercepted Mullens and sprinted 76 yards up the sideline for the touchdown to expand Washington’s lead to 23-6. Although San Francisco crept back in the game with a 75-yard scoring drive that it capped with a two-point conversion, the defense held up enough to thwart disaster.

The 49ers, who have been temporarily displaced by coronavirus-related restrictions in Santa Clara County, were the designated home team for the rare neutral-site showdown.

Haskins, in his first game since Week 4, played the entire second half for Smith and showed much of the same up-and-down play that derailed his start to the season, going 7 for 12 in the half with 51 yards and a 68.4 rating.

After guiding Washington to a 72-yard scoring drive that ended with Dustin Hopkins’s third field goal of the day (21 yards) at the start of the half, Haskins was nearly intercepted deep in Washington territory in the fourth quarter. Washington led by only eight points when 49ers safety Jimmie Ward appeared to pick off Haskins on a pass up the middle on a third and 10 from the 14-yard line. The initial call of an interception was overturned on review, when the replay showed the ball hit the ground before landing in Ward’s grasp.

A crisis was averted, and the defense held up. Afterward, Rivera reiterated another message to his players.

“We’re relevant. We’re in the conversation. People are talking about us, and we have to maintain and be humble,” he recounted to reporters. “We have to understand that. Like I told them about last week’s victory and now this week’s victory, this thing will carry us to the game, but it won’t be anything once we play the game. So we’ve just got to enjoy it and then get ourselves prepared for the next game that we play.”