The 49ers last season finished 19th in the NFL with 33 sacks and lack dependable edge rushers heading into 2017. And while they switch to a 4-3 defense that relies on a single safety deep, they don’t have an established defensive back to play center field, either.

Stanford defensive lineman Solomon Thomas was a strong fit as a five and three technique along the defensive front, boosting the pass rush from the interior in sub packages. But what Thomas doesn’t do is rush from the edges, leaving a void on the outside with 33-year-old Ahmad Brooks and the unreliable Aaron Lynch likely to man the outside.

The 49ers are trying 2015 first-round pick Arik Armstead at the coveted LEO position that rushes quarterbacks’ blind sides against left tackles. But Armstead may be a square peg in a round hole outside after playing as an interior 3-4 lineman both in Oregon and during his first two seasons in the pros.

Lynch in an ideal world would be the pick for LEO. He showed promise during his first two seasons as a pass rushing 3-4 outside linebacker but showed up to the offseason program last year some 30 pounds overweight while dealing with a four-game suspension to start the season. It led to the worst of his three years when he logged just 1.5 sacks after having 12.5 combined over his first two.

Lynch is entering a contract year and could make a ton of cash if he rebounds and lives up to his promise. But the 49ers couldn’t afford to bank on it, and they didn’t invest in a potential LEO until the sixth round of the NFL draft this week when they tapped Utah’s Pita Taumoepenu.

Taumoepenu has upside but needs development before he can challenge Lynch and the team’s other pass rushers for their jobs. This was a draft rich in pass rushers and the 49ers didn’t land a true LEO in the early rounds. If Lynch doesn’t have a good season, it could hurt them.

At safety, San Francisco likes the idea of Jimmie Ward converting from cornerback. He could flourish in the role given he played there in college. But that was four years ago. He’s coming off a broken collar bone and had a pin surgically inserted into his foot after two Jones fractures. He’s missed 13 games in his first three seasons due to injury.

Given the value of the position, playing Ward at free safety brings considerable risk. The 49ers would have been wise to address the position with an early-round draft pick. But they didn’t, and don’t have a viable option at free safety should Ward go down again.

To be fair, the 49ers entered the draft with needs at nearly every position. It was impossible to fill every void with one draft class. And while the class was strong overall, new GM John Lynch new coach Kyle Shanahan missed two important areas in their first draft.