What is the 49ers biggest weakness heading into the playoff stretch?

A week ago, we talked about the San Francisco 49er’s greatest asset heading into their playoff run. I said it was as simple as the team’s ability to field better players than their opposition. The talent on this roster is being put in a position to succeed, but when you look at some of the other rosters, the 49ers are stacked at the positions you need to have talent at. Despite all the injuries, that still rings true. My second point was Kyle Shanahan’s ability to dial up the big play, and the defense’s knack for limiting explosive plays. It’s a bit of the best of both worlds, and that has gone a long way in San Francisco’s success this season.

What about the flip side of this question? What is the Niner’s biggest weakness as we get into the playoff run? What will be the thing that ultimately dooms San Francisco when it matters the most? Here is one option for both sides of the ball.

Struggles on money down

In the last month, the 49ers offense has converted 18 of their 48 third downs. That 37% clip would rank San Francisco around 20th in the NFL this season. The offense is trending in the wrong direction, as they’re converting 48% of their third downs on the season, which is good for sixth in the NFL. The 49ers converted four of ten third downs against the Rams. Two of those were the 3rd & 16 plays on the final drive, and another came when Jimmy Garoppolo made a great play near the goal line after scrambling and finding George Kittle for a touchdown.

At the moment, those plays are great. It’s naive to think the offense can continue to rely on spectacular plays on third down. Let’s use a couple of the third downs from the Rams game as examples. The first third and goal was simply a good play by the Rams linebacker. The play call and design was good. George Kittle ran a “shake” route down the middle of the field, but it was well defended, and Jimmy Garoppolo’s throw was incomplete. The next third down, the 49ers needed five yards to convert, but they threw a deep pass down the sideline to Kittle. That play never had much of a chance. The next missed third-down came on 3rd & 6, when Deebo Samuel only gained two yards on a screen pass.

What’s the issue? Second down.

San Francisco averages 6.5 yards per play on first down, which is the best in the NFL. On those third downs mentioned above, here is the yardage the offense gained on second down in the first half against the Rams: 0, 1, 1, 0, 0, 0, 15. I’m not even sure how you explain what is happening on second down, but it’s not good. The best way to convert on third down is to avoid having one. The offense needs to give themselves a better chance before they reach third down.

Lack of red zone resistance

Opposing offenses have reached the red zone 12 times in the past four games. Those teams have scored 11 touchdowns. Heading into December, this was the strength of the 49ers defense. The unit was third in the NFL at 41%. With the struggles in the red zone during December, the Niners are down to 17th in the league, allowing 58% of red zone drives resulting in touchdowns.

Injuries have undoubtedly contributed to this, which has led to more mental breakdowns. Take Cooker Kupp’s touchdown, for example:

All season, the 49ers have run “Cover 1 Thief” in these situations. What that means is the free safety is diving on all crossing routes. The alignment by the Rams makes it impossible for Ahkello Witherspoon to get inside leverage and prevent Kupp from crossing his face. Still, the issue is free safety Marcell Harris, who doesn’t relate to anybody. He’s just drifting, instead of keying on someone crossing the middle. In no way should Witherspoon have to run across the entire field and guard a receiver without any help.

Jimmie Ward, playing slot cornerback above, has been phenomenal at recognizing crossers all season and erasing those routes. There’s a reason Robert Saleh calls the position “the eraser” role.

Speaking of Ward, there first touchdown looked like it was on Witherspoon, but, by rule, it was on him:

It’s tough to be too upset at Ward there as he likely read Jared Goff’s eyes and went for the crossing route. That’s him playing football. Witherspoon isn’t out of the woods here, either. If he is going to bait Goff, which it looked like he did, he has to make the play. It’s as simple as that.

For much of the season, the 49ers would get a critical sack in the red zone that ended drives. Sacks have been hard to come by, especially near the goal line. Mental mistakes like the plays above, lack of sacks and turnovers, and poorly timed missed tackles have allowed offenses in the end zone. As the competition steps up, offenses are going to move the ball. The 49ers have to clean up their red zone defense if they want to make a playoff run.