When the San Francisco 49ers reached the Super Bowl following 2012, their three leaders in sacks – Aldon Smith, Justin Smith and Ahmad Brooks – combined for 29.

Last season, San Francisco as a team finished with 28, the third fewest in the NFL. The inability to pressure opposing quarterbacks played a role in finishing 29th in total defense, 27th against the pass and 26th in interceptions.

Presumably, one of general manager Trent Baalke’s mandates this offseason was to improve the struggling pass rush to make things easier on a young secondary that’s built on a number of early-round draft picks, including safeties Eric Reid (first round, 2013), Jimmie Ward (first round, 2014) and Jaquiski Tartt (second round, 2015). This year, Baalke used third- and fourth-round picks on cornerbacks Will Redmond (Mississippi State) and Rashard Robinson (LSU).

“The key to me to playing defensive football is third down. Get off the field on third down. And build your roster so you can get off the field on third down,” Baalke said.

“You got to be able to stop the run and you got to be able to rush the passer. If you can do those two things, third down becomes a lot easier.”

With a few rare exceptions, the NFL’s best pass rushers come from the edge, where Baalke didn’t add a player of significance with some $50 million in cap space or 12 draft picks this spring.

The 49ers enter the summer with Aaron Lynch, Brooks, Eli Harold and Corey Lemonier rushing from the edges at outside linebacker and defensive end on passing downs. Lynch and Brooks tied for the team lead with 6.5 sacks each last season, modest totals, while Harold and Lemonier did not have any.

Baalke is hoping improvement in the pass rush in 2016 comes with two rookie additions along the defensive line and returning players adapting to more prominent roles.

First-round pick DeForest Buckner figures to provide a significant boost from the inside after registering 10.5 sacks last season at Oregon. His former college teammate Arik Armstead had 2.0 as a rookie and will see his capacity increase while last year’s starters Ian Williams (ankle) and Glenn Dorsey (knee) face uncertainty surrounding their injuries.

Fifth-round pick Ronald Blair is earmarked to rotate in as a reserve after notching 21 sacks at Appalachian State. Quinton Dial (4.5 career sacks), Tank Carradine (4.0) Tony Jerod-Eddie (zero), Kaleb Ramsey (zero) and Mike Purcell (1.0) round out the defensive line.

The key in San Francisco’s ability to bother quarterbacks could come in the evolution of two players: Carradine and Harold.

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Carradine has slimmed down more than 20 pounds to the 270s and will work on the edges as a defensive end in the team’s four-down front for passing situations.

That’s similar to the position he played at Florida State as a 4-3 defensive end, when he was viewed as a first-round talent before suffering an ACL tear in his final season. Carradine, 26, was drafted in the second round in 2013 to line up over guard to eventually replace Justin Smith, but saw minimal production at that position during his first three seasons and began the transition to his new role last year.

Harold, 22, has his weight up toward 270 after he was pushed around by opposing tackles as a string bean rookie weighing in the 240s. He might be the most important player in the defense’s quest for more sacks, while Brooks recently turned 32 and has seen his production decline over the last two seasons.