In their game at San Francisco in Week 14, the Tampa Bay Buccaneers' defense saw something it doesn't encounter on a regular basis: a fullback.
The 49ers used the traditional "21" personnel grouping on 36 of their 59 offensive plays, which is the term used for a package featuring two running backs, one tight end and two wide receivers. They ran four other plays with different combinations that included two running backs. In the Buccaneers' first 12 games combined they had run a total of 60 defensive snaps against 21 personnel, or just five per game. Their last four opponents had used that grouping for a grand total of three plays.
The 21 grouping doesn't have to include a traditional fullback; the Buccaneers have run a small handful of plays this season with two of their tailbacks on the field at the same time. But the 49ers do have a traditional fullback in Kyle Juszczyk and they use him a lot. Against, the Buccaneers he was on the field for 41 of the 49ers' 63 offensive plays, just three fewer than starting tailback Christian McCaffrey. Overall, he has played 51% of the team's offensive snaps so far this season.
According to NFL Next Gen Stats, the 49ers found quite a bit of success with this personnel, gaining 243 yards and scoring two touchdowns out of the 21 package. They gained 6.75 yards per play, which is higher than their full-season rate of 5.78 yards. Interestingly, the 49ers were actually better in their more limited use of "11" personnel, which includes one running back, three wide receivers and one tight end. On those 16 snaps, the team gained 145 yards, or 9.06 per play, and also scored two touchdowns. In terms of "success rate*," however, the 49ers were equally good with those two options, at 56% for both. That suggests that the Niners were more boom and bust when they went three-wide.
(* A play is a success on first down if gains 40% or more of the yards needed for a first down; on second down, it's a success if it gains 50% or more of the yards needed; and on third down it's a success if it gets the first down. Kneel-downs are excluded.)
As a result, the Bucs stayed in their base 3-4 defense for the majority of the game, whereas the nickel package with five defensive backs is usually their most common grouping. The problem with that is Tampa Bay lost its Pro Bowl nose tackle just four snaps into the game, as Vita Vea suffered a calf injury almost immediately. That meant more work than usual for Will Gholston, Rakeem Nunez-Roches and Deadrin Senat, all of whom logged their highest or second-highest snap total in any game this season.
The Buccaneers were at the far other end of the spectrum, using 11 personnel on all but eight of their 74 offensive snaps, according to Next Gen Stats. The 35-7 final score makes it obvious that the Buccaneers did not find as much offensive success out of any grouping; out of the 11 package they gained 290 yards on 66 plays, or 4.39 per play, scored one touchdown and a 45% success rate.
In addition, Tom Brady worked out of the shotgun on 89.2% of the snaps, even on most of the running plays. The Niners' Brock Purdy, in contrast, ran exactly 27 plays out of the shotgun and 27 from under center, with a handful of other formations, including the pistol, which is another kind of two-back set. The Niners gained 7.22 yards per play and scored three touchdowns from the shotgun, compared to 5.22 yards and one touchdown from under center.
The Bucs use of the shotgun on 89.2% of their offensive plays was by far their highest rate of the season. in no other game have they even hit 75%. This may have been an effort to help Brady get rid of the ball quickly thanks to the presence of NFL sack leader Nick Bosa and a strong 49ers pass rush.
If the usage of 21 personnel played any factor in the 49ers' strong showing on offense, in and of itself, the Buccaneers don't have to worry about contending with it in their next outing. The Cincinnati Bengals, who come to town this Sunday for a Week 15 tilt, have not run a single play this season out of the traditional 21 grouping (two running backs, one tight end, two receivers). They have run a total of 22 plays that featured two running backs in some other groupings, but that only represents 2.% of their 849 offensive snaps overall.