The Seahawks hung with the NFC West-leading 49ers early in Thursday night's game, with both defenses playing tough, but a rough sequence in the second quarter allowed the 49ers to build a two-score lead, and while the Seahawks fought to the end, they couldn't quite recover from that early blow. The end result was a 21-13 San Francisco victory that allowed the 49ers to clinch the NFC West, dropping Seattle's record to 7-7 with three games left to play.

Here are five rapid reactions to Thursday night's loss:

1. A sequence late in the second quarter made all the difference.

With the 49ers leading 7-3 late in the second quarter, quarterback Brock Purdy fired a pass over the middle of the field and right into the path of Seahawks safety Quandre Diggs. It looked like a sure interception a player who has 15 of them dating back to the 2019 season, but the usually sure-handed Diggs was unable to corral the ball, meaning a punt instead of a turnover that made a big difference in field position.

Even so, the Seahawks still got the ball back at the 19-yard line with 1:48 left in the half and all three timeouts, and after driving for a field goal on their last drive, they looked to have a little something going on offense, getting a quick first down on passes to Tyler Lockett and Marquise Goodwin. After a Travis Homer run got 5 more yards, Geno Smith hit Homer for a 6-yard gain that would have given Seattle a first down, but a hard hit from Dre Greenlaw knocked the ball loose, and Charvarius Ward recovered, returning it 40 yards to the Seattle 6-yard line. Two plays later, Christian McCaffrey was in the end zone and the 49ers led, 14-3.

If Diggs hangs onto that pick, or if Homer hadn't fumbled, the Seahawks very well could have taken the lead heading into halftime, or gotten a field goal to make it 7-6, or at the very least, gone into the locker room down only four points. Instead, the turnover that wasn't and the one that was put the Seahawks into an 11-point hole, and with the 49ers adding onto the lead with a 54-yard George Kittle touchdown to open the second half, Seattle was never able to recover.

2. The 49ers defense is as advertised.

The Seahawks knew it was going to be tough to move the ball against a 49ers defense that came into the game ranked first in scoring defense, total defense and run defense, and while the Seahawks had their moments, overall it was a very challenging day against the NFL's top defense.

The Seahawks punted on their first five possessions before putting together a good drive that ended in a field goal in the second quarter. That momentum was quickly lost, however, with the aforementioned fumble on the next possession. The Seahawks did put together another field goal drive in the third quarter, but needing more scores to get back in the game, the offense couldn't get going against a pass rush that made life incredibly difficult for Geno Smith with the 49ers recording 3.0 sacks and nine quarterback hits.

Smith and the offense did rally for a late touchdown, with Smith hitting Noah Fant for a score to make it a one-score game, so it was definitely a better performance for a Seahawks offense that didn't score against the 49ers in Week 2—a special teams touchdown was Seattle's only score in that game—but it was still a challenging day against the 49ers defense.

Returning from an ankle injury that kept him out of Sunday's game, Kenneth Walker III ran hard and fought for some extra yards, but overall it was tough to get the ground game going, particularly while playing from behind, and he finished with 47 yards on 12 carries.

3. Big plays undid an otherwise strong defensive performance for the Seahawks.

The Seahawks came into the game knowing they needed to be better on run defense, and for the most part they did show a lot of improvement in that area. No, they didn't shut down Christian McCaffrey, who finished with 108 yards on 26 carries, 23 of which came on one first-quarter run, but after allowing 223 yards on the ground last week, there were definitely signs of progress, especially considering that the Seahawks were without Al Woods and lost his backup, Bryan Mone, to a first-quarter knee injury, leaving them with no true nose tackle for almost the entire game.

And other than the touchdown that came off a turnover that gave them the ball at the 6-yard line, the 49ers only scored on two of nine possessions prior to a final possession in which they ran out the clock.

But what progress there was for Seattle's defense was overshadowed by a few big plays that were huge difference-makers, most notably a pair of touchdown passes to a wide-open George Kittle. The 49ers opened the scoring with a 28-yard touchdown pass to Kittle that featured some nifty misdirection that got the Seahawks defense out of position and left the Pro-Bowl tight end open in the middle of the field for the score. Later in the game, Kittle again found himself wide open for a big gain, and after making a couple of defenders miss downfield, he ran into the end zone for a 58-yard score. Fellow tight end Tyler Kroft found himself open for a 28-yard catch later in the game, meaning 110 of Brock Purdy's 217 yards came on three plays.

And while the run defense showed a lot of improvement, the Seahawks did give up a 55-yard Jordan Mason run at the end of the game, allowing the 49ers to take a knee to finish off the victory.

4. Jason Myers just keeps making kicks.

Jason Myers has missed only one field goal this season, and that came after a high snap, and with two more field goals on Thursday, he has now made 21 straight since that lone miss.

Even more impressive has been Myers' accuracy from long range. With his 51-yard field goal in the third quarter—into the notoriously difficult north end of Lumen Field on a cold night, no less—Myers improved to 6 for 6 from 50-plus this season. With six field goals of 50-plus yards, Myers tied Steven Hauschka for the most 50-plus field goal in a season in franchise history.

5. Playing through injury again, Ryan Neal just keeps making plays.

Ryan Neal has been listed as questionable in each of the Seahawks' last three games, but even with a sore knee on a short week, the veteran safety was once again one of the defense's biggest playmakers. Neal, who seems to be in on just about ever third or fourth-down stop for Seattle's defense, had a great open-field stop of McCaffrey early in the game to force a punt. Neal, who finished with five tackles, also had an impressive pass breakup down the left sideline to deny a potential big gain.