Kyle Terada-USA TODAY Sports
The pass rush led by Justin and Aldon Smith significantly tapered off at the end of the 2012-2013 season.
As Niners fans know very well, the pass rush fell off a table after Justin Smith hurt his triceps in Week 15.
Before Smith got hurt, the Niners averaged 2.44 sacks per game. In their next four games and change, the defense only mustered only four sacks.
Even if it's just a coincidence that the drop-off happened when Smith got hurt, as Justin Smith believes, that trend is a scary one. The Niners defense thrived on pressure. Their secondary isn't full of lockdown coverage players, so when the front gets pressure, it makes up for the secondary's weaknesses.
Without pressure, opposing offenses have a much better shot at attacking a secondary that has some coverage problems.
The good news is that Justin Smith is ready to go for the 2013-14 season. So hopefully, that will help change a disturbing trend since his triceps tear.
The Niners also bolstered their defensive line. They signed nose tackle Glenn Dorsey and drafted Tank Carradine, though Carradine is missing time with a knee issue. They also drafted Quinton Dial and re-signed Ian Williams.
So though they lost Isaac Sopoaga and Ricky Jean Francois, they still have depth up front. And specifically, it's good they have someone like Dorsey, who could do a better job filling in for Smith should he get hurt rather than any one San Francisco had last year.
Between the guys up front and outside linebackers like Aldon Smith, Parys Haralson and Ahmad Brooks, the Niners need to make sure they can resurrect their lost pass rush.
It was a key to their defense, and during that stretch where the pressure evaporated, they allowed almost 30 points a game.
Kaepernick may be good, but he'd rather not have to put up five touchdowns a game to win.
So watch what the Niners do in the preseason. See if they blitz more, rush outside linebackers more or if Justin Smith seems like his normal self. This pass rush should be problem one, and you can bet Harbaugh has done something to address it.
Yet another thing to keep an eye on during the next three preseason games.