Redskins.com's Stephen Czarda provides five things we've learned about the Washington Redskins in games in Weeks 6-9 -- 49ers, Eagles, Cowboys and Seahawks -- of the 2017 regular season.

1. The Redskins' depth has been tested off the last four weeks, particularly along the offensive line.
While the Redskins had the same starting offensive line intact for the first four weeks of the season, Washington's look up front has significantly changed over the last few weeks.

First, both Pro Bowl left tackle Trent Williams (knee) and third-year starting right tackle Morgan Moses (ankles) battled injuries before center Spencer Long (knees) and guards Brandon Scherff (MCL sprain) and Shawn Lauvao (stinger) showed up on the injury report in recent weeks.

Swing tackle Ty Nsekhe also has been sidelined since Week 3 with a core muscle injury that required surgery.

During the Redskins' Week 9 victory over the Seahawks, Williams, Long, Scherff, Lauvao and Nsekhe all weren't healthy enough to play. With the bevy of injuries, the Redskins had T.J. Clemmings, Arie Kouandjio, Chase Roullier and Tyler Catalina as starters alongside Moses.

Clemmings, Roullier and Catalina are all in their first seasons with the Redskins while Kouandjio rejoined Washington's roster before the Dallas game after being waived during September roster cuts.

"They're playing together for the first time, really," said Redskins head coach Jay Gruden. "T.J. is doing a good job, he's getting better. Tyler is getting better. Obviously Chase [Roullier] is doing a good job at center. So it's just about communication, playing together, trying to play in unison, which is hard to do at this stage of the season, but I think Coach [Bill] Callahan and Coach [Kevin] Carberry are getting them ready to go."

The Redskins could return a few of the injured offensive linemen as early as this week, as Gruden noted that they could increase their practice loads depending on how they feel getting back to physical activity. One player to keep an eye on, though, is Williams, who is hoping that rest will ease the pain in his injured knee.

Williams played through the pain in Washington's games against San Francisco and Philadelphia, but has been inactive the past two games.

The five-time Pro Bowler desperately wants to be on the field, but he's also thinking about his long-term health as he weighs the option of eventually getting surgery.

"If I want to play the career I think I can play and play well into my early- to mid-30's, I would probably have to get it at some point, just being honest, totally honest about the situation," Williams said. "I can gut it out, but it's just not that safe for me, speaking longevity-wise. You've got to think, if I'm 29 now and I put it off for a couple more years, your body just doesn't heal the same when you're entering that third decade of life.

"So, you've got to weigh that type of decision out too. But, it's difficult, sitting there watching games, because I know that I can help my team in some capacity. It's tough, man, it's tough. I've never been in a situation like this."

2. Ryan Kerrigan continues to be the Redskins' most consistent pass rush threat.Sometimes it's easy to forget just how steady Kerrigan has been for the Redskins since being selected with the No. 16-overall pick in the 2011 NFL Draft.

The Purdue product has started all 104 of his regular season appearances since his professional debut, longest active streak among NFL linebackers. He's also 1.5 sacks away from becoming only the fifth player in NFL history to record 7.5 sacks for seven straight seasons to open a career, joining Pro Football Hall of Famers Reggie White and Derek Thomas along with two four-time first-team All-Pros DeMarcus Ware and Jared Allen.

Over Washington's last four games, Kerrigan has 3.5 sacks including a pair off Cowboys quarterback Dak Prescott in Week 8. Kerrigan dominated Dallas' vaunted offensive line for much of the afternoon.

While Kerrigan didn't record a sack against the Seahawks this past Sunday, he was still able to get pressure on Seattle quarterback Russell Wilson for much of the afternoon despite the offense targeting him as a key player.

"You've got to worry about Ryan," said Seahawks coach Pete Carroll. "He is really an effective player. He's a problem every snap, run and pass. He's such an aggressive player that's a guy that we're really tuned in to."

3. Vernon Davis hasn't aged a bit while Josh Doctson is starting to come into his own.
Although Chris Thompson's breakout season has turned heads around the league, Davis has provided the Redskins quite the No. 2 passing option at the tight end position.

Through eight weeks of the season, the University of Maryland product is second on the Redskins in receiving yards (384) while currently ranking No. 7 in average yards per reception at nearly 17 yards.

In Washington's last four games, the 12-year veteran has caught 15 passes for 224 yards. His production has come at a time for need, as the Redskins were without both Jordan Reed and Niles Paul against Seattle.

When one or both returns, it will only help Davis as the Redskins excel in two- and three-tight end packages.

"Vernon, he's a very talented player," Reed said. "Very explosive, so when both of us are on the field, one of us is going to have a matchup that can be taken advantage of and I think that's where it comes into play."

As for Doctson, Washington's first-round pick in the 2016 NFL Draft is beginning to show flashes of the player that was so high on the draft board.

After being held without a reception for the first two weeks of the season, Doctson recorded a 52-yard touchdown catch on his first grab of the season against the Oakland Raiders.

The tide really started to turn after the Philadelphia game in Week 7, though, as Gruden made it known that Doctson's target were going to increase.

"Josh Doctson has emerged, to us, in practice that he deserves more reps," Gruden said late last month.

The 2015 unanimous All-American made perhaps the play of his young career against the Seahawks, a diving 38-yard grab that set up the Redskins' game-winning score.

More plays like that will give quarterback Kirk Cousins the confidence to target him in key situations.

"He's got a chance to be a great player in this league," Cousins said. "We just have to continue to develop him and then give him opportunities. It's still very early in his career; he's pretty much halfway through what would be his rookie year. It's exciting to think what could be down the road, but have a lot of work to do to get there."

4. After a difficult rookie season, Kendall Fuller looks like a completely different player.
There weren't many questions about Fuller's potential going into the pre-draft process, but the Virginia Tech product's college career ended abruptly by a torn ACL.

The recovery from that injury spilled into his rookie season, as he was slowly eased into action but still wasn't quiet at full percent for most of his debut campaign.

This year has been a different story for Fuller, though, as he's already recorded three interceptions including a game-sealing pick against the 49ers in Week 6 that locked up the Redskins' third victory of the season.

"I just told him big players make big time plays in big time situations and he did that," said safety D.J. Swearinger at the time. "He had been yelling out the whole game that we were going to make a play to win and he did that. So, that's a great job by Kendall."

Then against the Seahawks, Fuller perfectly jumped Doug Baldwin's slant route for his third interception of the season.

"I think in the series before, I kind of jumped the out route, and…they probably went to the sidelines because I was playing heavy outside before," Fuller said. "He made a check and I just kind of felt like they were going to run an inside-breaking route and just made a play."

5. Kirk Cousins has been steady behind center despite all of the moving parts around him.
Only one player has been in on every offensive snap for the Redskins since the 2016 regular season opener, and that's Washington's starting quarter.

Over the last four weeks, Cousins has lost multiple offensive linemen to injuries, his starting running back has been slowed by injuries of his own, two of the tight ends went down against the Cowboys and even Jamison Crowder was out last week.

Washington has also experimented with the workloads of Doctson and Terrelle Pryor Sr. as both play the X receiver position.

But since the Bye Week, Cousins has been very similar to the quarterback who earned the right to start in 2015. Over the last four weeks, the Michigan State product has completed 102-of-147 passes (69 percent) for 1,143 yards with six touchdowns to three interceptions.

His season-long quarterback rating of 102 is seventh-best among regular starters.

Although Cousins was unable to lead a potential game-tying drive against the Cowboys in Week 8, the Pro Bowler led a game-winning drive against the Seahawks in Week 9.

After Seattle took a 14-10 lead just after the two-minute warning, Cousins led a four-play, 70-yard scoring drive on an afternoon when the offense struggled to move the ball.

"The resilience that he showed to make those two big throws at the end of the game was a great tribute to him and how mentally tough that he is," Gruden said. "Any time you go to Seattle and get a win, I don't care how you do it, you know, what your stats look like, how many times you got hit or get sacked, to get a win over there and have a key two-minute drive, you know, to get it done is impressive. So we're obviously proud of the fact we got it done and Kirk played very well."