There is no doubt that the San Francisco 49ers are significant favorites to win the NFC Championship against the Green Bay Packers and advance to Super Bowl LIV. At the time of writing, Vegas has the line at 7.5 points, and though PFF Greenline has it a little closer, the data still says the 49ers are worth around a touchdown this weekend.

One takeaway from these playoffs, particularly in the divisional round, is that football is a game of fine margins; random chance and huge plays can dramatically swing the outcome. A 7-point line says the 49ers are a markedly better team than the Packers, but one pick-six and it’s suddenly a coin flip, and that’s why it’s worth exploring quarterback Jimmy Garoppolo‘s tendency to make major mistakes with the football.

Including the playoffs, Garoppolo has 14 interceptions and 21 turnover-worthy plays (TWP) by PFF’s charting. His turnover-worthy throw rate isn’t among the worst in the league, but only 13 quarterbacks put the ball in harm’s way more often, and it’s by far the worst rate of any of the remaining quarterbacks on championship weekend.

Turnover-worthy play rates among remaining quarterbacks (2019 season, including postseason)

Rk Name ATT BTT TWP TWP % 1 Aaron Rodgers 642 39 16 2.49% 2 Patrick Mahomes 580 32 16 2.76% 3 Ryan Tannehill 335 23 10 2.99% 4 Jimmy Garoppolo 526 15 21 3.99%

Garoppolo also doesn’t offset that danger with a significant amount of big-time throws (BTT), the highest-graded throws in PFF’s play-by-play grading. He has just 15 of those (compared to 28 touchdowns this year) and fields the sixth-lowest big-time throw rate in the NFL. This isn’t to say he is a bad quarterback, and the scheme in San Francisco with Kyle Shanahan at the helm is one of the best in football at creating positive passing plays that Garoppolo can take advantage of, but it does start to articulate the kind of quarterback he is.

The term “game manager” has become something of a pejorative for quarterbacks, but to me, it simply describes a style of passer who doesn't add significant value through a volume of big throws outside of the structure of the offense but is capable of taking what is on offer with solid efficiency. For me, Garoppolo fits broadly into that bucket, but what complicates his play is his propensity to make more mistakes with the football than a typical game manager.

It occurred to me while watching the 49ers beat the Minnesota Vikings this past week, as Garoppolo seemed intent on making Vikings linebacker Eric Kendricks his favorite target on the day, that Garoppolo also tends to have a specific style of mistake with the ball. Certain quarterbacks seem to struggle to see linebackers at the intermediate level. Whether it’s failing to recognize them dropping into a zone underneath, not seeing them read the play and come across the formation or simply being locked in too tightly on the coverage behind them and not even registering them as an obstacle that needs to be navigated, some quarterbacks consistently struggle to avoid throwing them the football, and Garoppolo is one of those passers.

As an example, take the first pass he tried to put in the hands of Kendricks this past weekend. This is an excellent play by the Vikings linebacker, but it was certainly clear before the moment Garoppolo committed to the pass that the geometry didn’t add up and that Kendricks was running the route more than George Kittle was. In the end, Kittle had to turn defensive back and break up the pass to save an interception, only to find his quarterback go back to the Kendricks later in the game, this time for a pick.

This was just a gut feeling I had about Garoppolo and how he reminded me of some other quarterbacks, but it turns out it’s backed up by the numbers. Using PFF’s database, we can start to dial in on the situations where Garoppolo is testing intermediate coverage. If we filter out anything behind the line of scrimmage or deep (20-plus air yards), Garoppolo has a turnover-worthy play rate of 6.9% when throwing into coverage of linebackers, almost 2.5 percentage points higher than his rate targeting all other positions in the same areas.

What’s interesting is that the NFL average works in the other direction. The league-wide average turnover-worthy play rate on throws into the coverage of all non-linebackers is 4.1%, but when throwing the ball at linebackers, it drops to just 3.0%. While most quarterbacks become less likely to make turnover-worthy mistakes when picking on linebackers, Garoppolo sees his likelihood spike.

Garoppolo has been a pretty efficient quarterback running Shanahan’s offense, and he has shown that he is capable of big games where he adds significant value to the system and playmakers around him, but over the regular season, he ranked just 13th in overall PFF grade. He had as many games with a grade in the 40.0s as he did in the 80.0s, and the team has been dominating without the need of a quarterback playing out of his mind, like some of the other teams still in the playoffs.

While going up against All-Pro caliber players such as Eric Kendricks will amplify the problem, Garoppolo’s propensity to not see linebackers over the middle exists regardless of who's in coverage. Sure, elite players at the position will force themselves into throwing lanes more often, but even players like Green Bay’s Blake Martinez can catch a pass if one is thrown right to him.

The 49ers are strong favorites against the Packers, but that margin could evaporate in an instant if Garoppolo continues to misread what's in front of him. The 49ers passer has been an important part of this run towards the Super Bowl, but a tendency to make mistakes with the football could swing the balance at any time. Against the Vikings, those mistakes weren’t enough to overcome the team’s overall superiority, but if they happen again against Green Bay, will the same thing be true?