The discomfort was instant. As Chicago Bears quarterback Justin Fields sprinted to his right Sunday, Las Vegas Raiders defensive end Yannick Ngakoue caught him from behind, tangling Fields’ feet and causing his stride to become discombobulated. Fields’ left leg planted awkwardly in his attempt to break free, and he went down hard.

His left knee was in significant pain.

“I knew I hyperextended it,” Fields said.

Fields slowly pulled himself up but hobbled to the bench. Andy Dalton came onto the field.

The collective gasp from Bears fans was felt across Allegiant Stadium in Las Vegas.

Yet just a few minutes later, Fields tested his leg while jogging on the sideline, refocused and charged back into the game. He missed only three snaps.

Of all the encouraging developments for the Bears in the energizing 20-9 road victory, Fields’ avoidance of serious injury and ability to play through discomfort deserve special mention.

“That son of a buck is tough,” Bears coach Matt Nagy said. “He’s proven that when he was in college. He proved it out here.”

If the entirety of Week 4 was a measure of Fields’ mental fortitude, challenging him to move past the pronounced offensive failures in the Bears’ 26-6 loss in Cleveland, then Week 5 tested Fields’ physical toughness. He had the wind knocked out of him on a first-quarter run, then hurt his knee two possessions later.

None of it rattled him. He was determined to play through the discomfort and remained dialed in on keeping the offense steady.

“When you’re in the moment, you can’t think about what’s hurting,” Fields said. “You just think about executing that (next) play.”

From a statistical standpoint, Fields’ efforts were far from spectacular. He threw for just 111 yards and added only 4 on the ground. The highlight-reel moments were few and far between. Still, in a charged-up road environment, Fields’ grit was obvious.

“That’s the No. 1 thing I’m taking out of this,” Nagy said, “is his toughness.”

Two weeks in a row now, Fields has shown a level of toughness that has won over coaches and teammates. His response to adversity between his first and second starts helped the Bears rebound and beat the Lions 24-14 in Week 4. He followed Sunday with impressive poise and sturdiness, battling through pain and helping push the Bears past the Raiders.

Fields’ physical talents are undeniable. He has top-tier speed, a strong, accurate arm and a feel for the game that will aid his ascent. But in two short weeks, he also has supplied evidence that his resolve and dependability are high-level qualities that can help him become a championship-winning leader.

Here’s our Week 5 QB rewind.

Defining moment

Before his career is finished, Fields will have much longer and far more impressive touchdown passes than the 2-yard dart he threw to Jesper Horsted in the second quarter. It was the rookie’s first career TD pass and only scoring throw to date.

Still, don’t underestimate the signs of promise within that sequence. The Bears faced second-and-goal from the 2 and called a play-action rollout. With linebacker Denzel Perryman slipping off coverage and charging hard at Fields, the Raiders’ pressure was more significant than anticipated.

Noticing that defensive back Amik Robertson had his back turned, Fields made a quick risk-reward calculation and a decisive throw as Perryman barreled toward him. Fields released the ball a half-beat before getting drilled.

“I knew (Robertson) couldn’t see the ball,” Fields said. “So I just threw it up and gave Jesper a chance. … Just put it where the defender isn’t.”

Horsted was running a corner route but adjusted to the unforeseen chaos, slowing his route and making eye contact with his quarterback while trying to create a window of opportunity.

“All Justin can see is where my eyes are going,” Horsted said. “So anything above the shoulders is going to be where I want the ball.”

Fields fired the football just above Horsted’s right shoulder, out of harm’s way and into a spot where a touchdown was possible.

“On the money,” Horsted said. “Good ball.”

Nagy was thrilled Fields had the presence of mind to take a calculated chance rather than just throw the ball away because Horsted wasn’t open.

“That,” Nagy said, “is growth for him.”

On the bright side

The Bears, after entering the game with the league’s worst third-down conversion rate at 28.9%, had their best day of the season in that category, converting 6 of 13 attempts. They ran off a surge of five consecutive third-down conversions in the second quarter, including four on their second touchdown drive.

Perhaps most notable in that series was Dalton’s 8-yard completion to Marquise Goodwin on third-and-7 from the Raiders 43. Coming in cold off the bench, Dalton diagnosed zone coverage, saw Goodwin sit down in a soft spot and drilled a completion. That moved the chains and extended a critical TD march.

Fields’ most significant third-down throw was his 13-yard completion to Darnell Mooney on third-and-12 during the Bears’ penultimate scoring drive. If the Raiders had gotten a stop, they would have gotten the ball back with 7 minutes remaining, trailing by five.

Fields, however, saw the Raiders dropping into coverage with five defenders backed up to the first-down line. His first option was Mooney and he made a decisive throw — on time and on target.

“Just get the first down. That’s all I’m thinking,” Fields said. “Stay in the pocket, find a way to get the first down.”

That pass required crisp timing and precise ball placement. Mooney ran a sharp route out of the slot and went down to make a nice catch.

“All week, we had that bad boy sitting there waiting for that moment,” Nagy said. “It’s one of those crucial third-and-12s. That was a big-time play in that game. If you don’t get that, now the momentum meter swings to them big time.”

The Bears chewed up 32 more yards after that completion and finished the possession with a 46-yard Cairo Santos field goal to take a 17-9 lead. That was a clutch offensive contribution at a critical juncture.

Fields completed both of his pass attempts on the series and had another throw to Allen Robinson that netted a 14-yard pass interference penalty. Ten plays, 57 yards, 6:16 milked off the clock. That’s winning football.

Uh-oh

Two months ago, when Fields scrambled and attempted a spin move on Miami Dolphins cornerback Nik Needham during the preseason, he was hit hard and fumbled, the kind of lesson a rookie quarterback ideally learns early and figures out how to avoid such missteps. Immediately after that game, Fields promised to remove that trick from his running repertoire, aware of how it put both his body and the football at risk.

“After that,” he said, “I think I’m going to officially retire the spin move.”

An understandable goal on multiple levels. Last January, with a similar spin during a College Football Playoff victory over Clemson, Fields was hammered by linebacker James Skalski on an 11-yard scramble and immediately experienced significant pain in his ribs, right shoulder and right hip.

During training camp this summer, Fields admitted he still was “scarred” from that hit.

“Literally every time I tuck the ball down and run, I’m thinking about getting out of bounds or getting down,” he said then. “There are of course going to be times when you have to try to fight for extra yardage. But I’m definitely smarter and trying to protect myself more.”

Sunday’s game presented one of those moments when Fields was trying to fight for extra yardage to convert on third-and-4. On the Bears’ second possession, he took off on a quarterback draw and tried spinning past safety Johnathan Abram.

Abram drilled Fields and took the wind out of him. Fields was visibly shaken on the sideline.

“I couldn’t really breathe, to be honest with you,” he said.

So, uh, Justin. You said you were going to ditch the spin after that Clemson shot last winter, yet Sunday’s spin and hit looked eerily similar.

“Man,” Fields said, “you’re telling me. I don’t know. I have no comment on that.”

Going forward, Fields and the Bears might have to devote extra attention to making sure the big hits he absorbs when running don’t diminishhis eagerness and instincts to run when merited. That can become a difficult balance.

“At this level,” Nagy said, “things are faster and they hit harder.”

That said, Nagy saw Sunday’s hit as situational with Fields striving to pick up a first down. He wasn’t being reckless.

“Some of those are going to happen,” Nagy said. “You want to be smart. But he has a good feel for that.”