LANDOVER, Md. -- Finally given a chance to chase quarterback Case Keenum in the midst of Sunday's torrential downpour, San Francisco 49ers rookie defensive end Nick Bosa blew past his would-be blocker and dropped Keenum for an 11-yard loss as the clock ticked to zero.

Without much thought, Bosa jumped to his feet, took a couple steps and dove headfirst toward Washington's sideline, sliding for about five yards and making a "mud angel" when he finally came to a stop. Bosa's impromptu celebration sparked a trend, as he looked over his shoulder to see most of his teammates joining in.

“It was a lot of fun," defensive tackle DeForest Buckner said. "It was definitely worth it. I saw Bosa out there sliding, so I said, 'Let's do it.' Everybody else started sliding around and everything. It was like a bunch of little kids out there. That's part of the game, having fun. Right now, we're having a lot of fun."

Indeed, there's no shortage of fun to be had for the 6-0 Niners -- especially on a defense that is proving that it's one for all seasons and conditions.

Entering the 9-0 win against the Washington Redskins, the 49ers defense had already established itself as one of the league's fiercest units. The Redskins didn't figure to offer much of a test but when Mother Nature intervened, Sunday's game suddenly became one of the most difficult tests of the season.

Earlier in the week, the Niners began planning for the rain, but there's only so much they could do in sunny Santa Clara to prepare. Each time Bosa checked Sunday's forecast, he saw a 100 percent chance of precipitation. From that, he knew this game could be the kind where the first team to score wins. He was right.

"We knew it was going to be muddy," he said. "We knew it was going to be slippery, so we knew we needed to have the offense's back so that's what we tried to do."

To say the Niners' defense has had the offense's back this season is a massive understatement. On Sunday, Washington mustered only 154 net yards of offense and averaged 3.8 yards per play. After an opening drive in which the Redskins ran the ball successfully -- much like the Rams did a week ago -- the Niners mostly shut them down.

San Francisco holding Washington to no points and 154 yards marked the third consecutive game in which the 49ers held an opponent to seven or fewer points and 200 or fewer yards. According to the Elias Sports Bureau, that makes them just the sixth defense to do that since 1990, a list that includes the famous 2000 Baltimore Ravens unit.

It was also the third straight game the Niners posted three or more sacks, the first time they've done it since Weeks 15-17 of 2011. And the shutout was the team's first since Week 1 of 2016, meaning the 49ers have surrendered just 10 points total the past three games. That's the fewest they've allowed in a three-game span since Weeks 14-16 of the 1987 season.

In other words, when kicker Robbie Gould nailed a 28-yard field goal with 5:28 left in the third quarter to break a scoreless tie, the game was all but over.

"It definitely puts you at ease, especially knowing how that game was going to be," coach Kyle Shanahan said. "You know both teams are going to eventually try for a big shot, so you know you have to commit to the run, just hold on when they take their shot and we're going to keep them from getting those plays, and we got a couple on offense and that was the difference between winning and losing."

Even on the rare occasion when the Redskins did threaten, the 49ers found a way to get a key stop with -- stop me if you've heard this one before -- a little-used backup stepping up in a key situation. This time, it was second-year defensive lineman Jullian Taylor.

Pressed into action by a hamstring injury to starting nose tackle D.J. Jones, Taylor came up with a run stuff against Washington running back Adrian Peterson on fourth down at the Niners' 28 in the second quarter, then made the first fumble recovery of his career after linebacker Kwon Alexander stripped Peterson with 1:29 left in the third quarter. All this in just six snaps.

"It says we have a tremendous amount of depth," cornerback Richard Sherman said. "Jullian is a great player and came through in a crucial situation and played in the clutch. He hasn't played in a few games. That's what you need on a great team is you need guys to always stay ready. You never know: next man up, next man up, next man up mentality."

After the game, Taylor called it a "privilege" to be with this team and defense. Through six games, it's easy to see why, as the Niners rank first in the NFL in yards allowed per game (223.5) and second in points allowed per game (10.67). For the season, they've allowed just 64 points, the second-fewest allowed through the first six games in franchise history.

With numbers like that, the 49ers defense has to feel like it's up for any challenge, even the difficult one next week against the Carolina Panthers and running back Christian McCaffrey.

"We always feel like it's on us," Sherman said. "We try to do our best to allow the offense to lean on us. And today was one of those days."

As Ray Charles might say, that's true, come rain or come shine.