ORCHARD PARK, N.Y. -- Buffalo Bills rookie cornerback Ronald Darby leads all NFL defensive backs with eight passes defensed through three games.

"I don't know if there is a rookie corner playing better than him," coach Rex Ryan said Monday. "Kid from Kansas City is playing pretty good. But [Ronald] Darby is doing a tremendous job."

Ryan was referring to Chiefs rookie cornerback Marcus Peters, the 18th overall pick in May's draft.

Like tackles, passes defensed can sometimes be a deceiving measure of performance because cornerbacks who are targeted less often by quarterbacks will naturally have fewer passes defensed.

Yet it's also a sign that a cornerback, even if beaten off the snap and targeted by a quarterback, is able to recover and stop a receiver from making a play.

In Darby's case, is his high volume of passes defensed a result of receivers gaining separation or just simply sound fundamentals when a quarterback is trying to force a pass toward Darby instead of in the direction of Stephon Gilmore, the Bills' top cornerback?

Let's investigate by looking at each of Darby's 10 passes defensed:

Week 1, first quarter: An inside motion by Phillip Dorsett caused Darby to take outside leverage on T.Y. Hilton; Darby played off the line and reacted well to Hilton's break in front of him. Verdict: On top of it.

Week 1, first quarter Darby was late to react to Hilton's break off the line and trailed by a step on a vertical pattern. However, Andrew Luck's pass was underthrown and Darby snagged the interception. Verdict: Good recovery.

Week 2, third quarter: Darby gave Julian Edelman a 7-yard cushion and reacted well when Edelman broke on his route. A late throw from Tom Brady sealed the deal. Verdict: On top of it.

Week 2, third quarter: Prior to the snap, Darby was repositioned by linebacker Nigel Bradham to take Danny Amendola in the slot. When Amendola broke inside on his route, Darby mirrored with two quick steps and smothered the pass. Verdict: On top of it.

Week 3, first quarter: Darby drew running back Damien Williams in coverage down the sideline and didn't allow him an inch of separation. Verdict: On top of it.

Week 3, second quarter: This was a highly questionable, errant pass from Ryan Tannehill under duress but credit Darby for reading Tannehill and finding the ball for his second interception of the season. Verdict: On top of it.

Week 3, fourth quarter: Darby got more help from Bacarri Rambo than he needed, as Darby blanketed Rishard Matthews down the field and likely would have intercepted Tannehill's well-thrown pass if Rambo didn't crash into Darby coming across the field. Verdict: On top of it.

Week 3, fourth quarter: On the Dolphins' final pass of the game, Tannehill launched a jump ball into the end zone off his back foot, underthrowing DeVante Parker in the corner of the end zone. Parker made a great adjustment to come back to the ball and Darby slightly over-ran the rookie receiver but was able to swat the ball out of Parker's hands. Verdict: Good recovery.