Football Outsiders looked at defenses facing different formations today, and there's one thing that jumps out at you about the Bucs numbers: they were pretty decent at defending most personnel groupings, except in one case: 3 WR sets. Whereas they ranked more or less as a middle-of-the-road defense for all of the other sets, the Bucs ranked 29th when facing 3 receivers.
There are a couple of reasons why is the case. For 5.5 games last season, if there were 3 wide receivers on the field, Elbert Mack or Myron Lewis was on the field as a defender. Elbert Mack should not be on an NFL roster, and while I like Myron Lewis' potential, he was not a good coverage player last season. So that explains part of the numbers, but not a lot of it.
For most of the rest of the season the Bucs had no such problem with their personnel. They countered 3-receiver sets with their nickel package, which had Aqib Talib, Ronde Barber and E.J. Biggers on the field. That's a pretty decent group of cornerbacks, and certainly not the 4th worst group in the NFL. E.J. Biggers is the weakest of those corners, and playing against Calvin Johnson for a game certainly hurt him, but he's still a decent outside cornerback.
So what happened then? Well, I'm not sure. Almost all of these 3-receiver sets featured a running back, which would explain some of this. The Bucs had some real trouble keeping track of running backs in the passing game, and they'd often be wide open underneath zone coverage.
In fact, the data supports this: of the 293 pass plays the Bucs faced in these situations, 64 were thrown to an uncovered receiver according to Football Outsiders game charting data. Uncovered players occur most often with running backs leaking out of the backfield, and on screens. The Bucs struggled against both last season. Only three of those passes were thrown farther than 4 yards beyond the line of scrimmage, and the vast majority were thrown behind the line of scrimmage. The Bucs must do a better job of defending screens and other throws that occur close to the line of scrimmage.
The most-targeted player on these plays was E.J. Biggers, though, with 48 targets. This may suggest that Biggers was not as solid as the games suggested. Teams clearly targeted him in passing situations, and seemingly with success.
Ronde Barber was targeted just 29 times, Talib just 26 times, and the opponent found a hole in zone 44 times. The remaining targets came mostly against linebackers, with all linebackers being targeted more or less at the same rate. Opponents also did a good job targeting defensive linemen on zone blitzes, finding them 9 times. Given the low frequency of zone blitzes, that's a pretty high number.