Football Outsiders recently showed some league-wide data on two different and opposite formations: formations with 6 offensive linemen (6OL), and formations with no one in the backfield (empty). These two formations are generally used for an entirely different purpose. 6OL sets are used to pound the ball down the opposition's throat, often in short-yardage situations. Empty backfields, on the other hand, are used when a team knows it's going to pass, doesn't care that the opposition finds out and just wants as many players as possible out on routes.
Interestingly, the Bucs did use a set with 6 offensive linemen relatively often compared to the rest of the league. They tried it 23 times, 17 of those times in short yardage. On those short yardage plays, the Bucs made the first down 10 times and failed to do so 7 times, which is a decent but not overwhelming result. The average gain on all these plays was 4.9 yards, while the 6 O-line sets in non-short-yardage situations averaged a whopping 11.3 yards per play. Those numbers are somewhat of a mirage, though, as the vast majority of the yardage came on one Earnest Graham 61-yard run. Overall the 6OL formation doesn't seem to have been of much use for the Bucs, but it was only used a handful of times and in specific situations anyway.
The empty backfield is a different animal, though. On average the NFL had a DVOA of 16.6% on these plays, making them much better than a replacement play. The masters of the empty backfield were Green Bay, New England and New Orleans. These three teams used an empty backfield on about 10% of all plays and were extremely successful in doing so, gaining 5.5, 7.2 and 8.6 yards per play respectively. The common denominator, of course, is that these three teams have an elite quarterback. So perhaps we can expect the same kind of success from the Bucs.
Unfortunately, this wasn't the case at all, as Tampa Bay lined up in an empty backfield just 1.8% of the time, and failed woefully on those plays with a 34.7% DVOA and an average gain of 5.5 yards per play. That last number may not seem too bad, but the situational data from Football Outsiders reveals that this was a very poor performance given the situations the Bucs were in when they used an empty backfield. The problems with this formation are legion, by the way: there's less flexibility in pass protection and the defense knows a pass is coming. Still, the high efficiency of the play suggests that good quarterbacks can compensate for the pass protection by getting the ball out to the open receivers. Perhaps we'll see more of this formation next season as part of Freeman's evolution as a quarterback.