When Rex Ryan's coaching staff took over in Buffalo last winter, they immediately sung the praises of Stephon Gilmore as a shutdown cornerback.
What they couldn't have expected was second-round pick Ronald Darby joining Gilmore as the league's best young cornerback tandem.
After taking home Defensive Rookie of the Month honors in September, Darby frustratedOdell Beckham in Week 4, preventing one of the league's most dynamic players from gaining separation.
"After I saw him that first practice, the way he moved around, I was like, 'Woah, he's a little bit better than what I saw on film,'" defensive backs coach Tim McDonald said this week, via Syracuse.com. "His change of direction, with how quick he is, is pretty unique. Combine that with his willingness to learn and work his ass off, he's been pretty impressive to me. ... He's been better than advertised."
Gilmore and Darby are so quick and so physical that it seemed every Marcus Mariota throw was contested last week.
Through five weeks, Darby and Gilmore rank second and third in Pro Football Focus' cornerback ratings, trailing only Carolina's Josh Norman.
Darby isn't the only greenhorn impressing. Here is Around The NFL's Rookie of the Year watch for Week 6:
1. Todd Gurley, St. Louis Rams running back: Much like Beckham a year ago, Gurley is a difference-maker with the unique talent to take the league by storm after sitting out the first month of the season. He's already leading the league in yards per carry (5.7) and runs of 20-plus yards (5) after moving the chains against a strong Packers defense.
2. Ronald Darby, Buffalo Bills cornerback: Opposing quarterbacks have posted a passer rating of 38.3 on throws in Darby's coverage. The only cornerbacks with lower ratings are Josh Norman, Darrelle Revis and Patrick Robinson.
3. Marcus Mariota, Tennessee Titans quarterback: As impressive as Mariota has been, the Titans have lacked big plays on offense. Although some of that can be attributed to subpar surrounding talent, Mariota needs to improve his sack rate and deep passing efficiency. Drew Brees is the only quarterback with a higher sack percentage, and Mariota has just two completions over 20 yards all season.
4. Amari Cooper, Oakland Raiders wide receiver: Coming off a tough matchup versus the Broncos' top-ranked defense, Derek Carr's go-to receiver is now on pace for 90 receptions, 1,235 yards and six touchdowns.
5. Henry Anderson, Indianapolis Colts defensive end: The third-round pick leads all 3-4 defensive ends in stops, Pro Football Focus' metric that measures any tackle that results in a "loss" for the offense. Anderson's 17 stops are five more than J.J. Watt's total through five games.
6. Leonard Williams, New York Jets defensive end: Williams, meanwhile, ranks second only to Mike Daniels among 3-4 defensive ends in Pro Football Focus' Pass Rushing Productivity metric that measures pressure created per snap played.
7. Jordan Hicks, Philadelphia Eagles linebacker: Hicks already has three fumble recoveries and is second on the Eagles with 34 tackles. "I know some people looked at us (and said) why are we drafting him in the third round?" Chip Kelly offered this week. "We thought we got a steal in the third round. He was our highest-rated guy for a reason."
8. Thomas Rawls, Seattle Seahawks running back: The undrafted free agent rushed for more yards in his fifth career game than Marshawn Lynch has managed in any of his 133 regular-season or playoff games. His 169 yards in Cincinnati are the most by a Seahawks rookie since Curt Warner's 207 in 1983. Rawls ranks among the NFL's leaders in yards per carry (5.6) and yards after contact per carry (2.86). This might be his only appearance on this list all season, as Lynch is due back from his hamstring injury to face the Panthers.
9. Hau'oli Kikaha, New Orleans Saints linebacker: Rob Ryan's defense is dead-last in the NFL despite promising performances from a trio of first-year players in Kikaha, inside linebacker Stephone Anthony and cornerback Delvin Breaux.
10. Vic Beasley, Atlanta Falcons pass rusher: Beasley was flat-out dominated by Redskins left tackle Trent Williams. As quick as he is off the edge, Beasley's smallish frame (6-foot-2, 235 pounds) works against him when he squares off against big, athletic linemen.
Watch list: Preston Smith, Damarious Randall, Marcus Peters, Ameer Abdullah, Tyler Lockett, Jameis Winston, T.J. Yeldon, Matt Jones, Melvin Gordon, David Johnson, Karlos Williams, Stephone Anthony, Shaq Thompson, Duke Johnson, Rodney Gunter, Frank Clark, Jamison Crowder, Ty Montgomery, Quinten Rollins
