In last Sunday's NFC playoff game between the Cowboys and Vikings, Brett Favre dropped back to pass late in the first quarter. As the Minnesota quarterback let the ball go, the Fox telecast switched to a shot of receiver Sidney Rice running up the right sideline. The ball dropped perfectly into Rice's hands as Dallas safety Gerald Sensabaugh was beaten in tight coverage. Touchdown, Vikings. On the replay, analyst Troy Aikman singled out Cowboys cornerback Terence Newman for not jamming Rice at the line. But Aikman was wrong—Newman didn't blow his assignment. This isn't a case, though, of the color analyst making a simple mistake. The bigger issue is that it's difficult for anyone to understand what cornerbacks do. That's because, even in the age of HDTV, it's often impossible to see the guys in the defensive backfield.
If you're a football fan, odds are you've cursed at the screen as the cornerback for your favorite team gets burned for a big play. Or so you think. At Football Outsiders, where we break down games to determine which players are stars and which are duds, we have a bunch of advanced metrics to help us assess a cornerback's skills: yards per play, stop rate, and success rate are but three among many. The trouble is that the traditional pre-snap camera angle gives us just a brief glimpse of corners before they disappear off the side of our flatscreens. It's even harder to track safeties. In the three years I've broken down televised games for Football Outsiders, I've never written about a safety because, as the defenders of the deepest part of the field, they rarely come into view.
So, how do we know how good these guys actually are? Darrelle Revis of the New York Jets is widely praised as the best cover cornerback in the NFL and for good reason—his technique in stalking and trailing receivers is spectacular. I know that because Revis plays a lot of man-to-man coverage: We can see him backpedal at the line of scrimmage and stick like Velcro to Randy Moss, Andre Johnson, and the rest of the NFL's elite receivers. A guy like Minnesota's Antoine Winfield, whose team plays more zone coverages that require him to play off the line five to seven yards, is a lot harder to assess because his screen time is more limited. Even with a player like Revis, we're left guessing when he leaves the frame. When I evaluate Revis' play, I rely on those first few yards, the occasional replay angle, and highlight shows like ESPN's NFL Matchup that show "coach's film" of all 22 players at once. Without steady access to this "all 22" tape, however, my views can't be conclusive, no matter how "forensic" I am in my analysis.
One guy who does have access to the tape is Greg Cosell, who's been the executive producer for various incarnations of ESPN's NFL Matchup shows since 1984. Cosell, who watches more "all 22" film than just about anyone not with a team, says that just about every type of coverage is difficult to discern from standard TV views. If "corners are close up at the line," Cosell explains, "they could obviously be playing man-to-man, or they could be playing Cover 2." The key to figuring out the coverage is to watch the interplay between the corners and the safeties—something that's impossible for home viewers to see since the safeties are entirely off the screen.
Cosell, armed with the coach's tape and a thorough knowledge of coverage concepts, was able to explain to me why Aikman was wrong about that Favre-to-Rice touchdown. Both the corner (Newman) and the safety (Sensabaugh) knew their assignments. Newman wasn't responsible for jamming anyone off the route; Sensabaugh was at fault for trying too hard to conceal the Cowboys' defensive tactics. "They rushed five; it was a zone blitz concept. They were playing zone behind it in coverage," Cosell explains. "[Newman] was responsible for [Vikings tight end Visanthe] Shiancoe first, then Rice, depending on the route. Sensabaugh was responsible for … Rice first, then Shiancoe. Sensabaugh disguised himself out of the coverage. He was responsible for getting over the top on Rice, but he was too late getting there because of the disguise."
Apart from the NFL giving fans and statistical analysts access to coach's film—and the league has shown no indication it wants to do that—we'll be at the mercy of analysts like Cosell to feed us these nuggets. Considering how tough it is to evaluate cornerbacks, we should consider ourselves lucky that Darrelle Revis' greatness is so obvious. We should also thank opposing quarterbacks for continuing to throw at the Jets corner. During the 2009 regular season, Revis was targeted 108 times according to Scouts Inc., the 5th-highest total in the league. The fact that the Jets led the league in Football Outsiders' opponent-adjusted metrics against No. 1 receivers raises the possibility that Revis might see half those targets next season. *
The league's true great corners, from Night Train Lane to Lester Hayes to Deion Sanders, didn't see many passes thrown their way because quarterbacks want to keep their jobs. Consider Revis' contemporary, Oakland Raiders cornerback Nnamdi Asomugha: He gets thrown at so infrequently that Football Outsiders had to lower its baseline for minimum number of targets per season so he could be included in our stat pages. We know of Asomugha's greatness more through his absence than through his presence. But even though we see more of Revis, that doesn't mean we're any closer to understanding what he's doing in deep coverage. For that, we'd need more time with the eye in the sky, and the pictures that reveal what's really happening on the field.
Correction, Jan. 22, 2010: This piece originally misstated the number of times New York Jets cornerback Darrelle Revis had the ball thrown in his direction during the 2009 regular season. Revis has been targeted 108 times according to Scouts Inc., not 65. (Return to the corrected sentence.)