49ers’ offensive potential unrealized in 2018 season

The San Francisco 49ers should have won seven games in 2018, according to head coach Kyle Shanahan.

They won just four, and lost all their road games for the first time since 1979. They fell “far short” of their expectations, according to GM John Lynch. But they have potential, if they figure out why they underperformed and where they must improve.

Here are the 49ers’ offensive grades for 2018.

The 49ers started three quarterbacks because two got hurt. Jimmy Garoppolo tore his ACL Week 3, and C.J. Beathard injured his wrist Week 8. Nick Mullens, the 49ers’ third-stringer, statistically was their best quarterback. His passer rating was 90.8. Garoppolo’s rating was 90. Beathard’s was 81.8. None of them ranked among the NFL’s top 20 quarterbacks. Combined, they threw 20 interceptions.

But all three essentially are rookies in terms of game experience. Each has made no more than 10 career starts.

Compared to other novices in 2018, the 49ers trio played quite well. All three posted higher passer ratings than Sam Darnold (77.6), Josh Allen (67.9) and Josh Rosen (66.7) -- rookies who were first-round draft picks. The only rookie quarterback who recorded a higher rating than Mullens and Garoppolo was Baker Mayfield (93.7), the No. 1 pick of the 2018 draft.

The 49ers have at least two of the best young quarterbacks in the NFL. If Garoppolo isn’t ready to play Week 1 next season, Mullens can run the offense very well. Other teams should be so lucky.

The 49ers signed starter Jerick McKinnon during the offseason to a fouryear, $30 million contract, but he tore his ACL before the regular season even started. His replacement, Matt Breida, played most of the season with an ankle injury and missed two games, but still averaged 5.3 yards per carry — fourthbest in the league among running backs with at least 100 rushing attempts.

Breida’s backup, Raheem Mostert, was even more efficient. He averaged 7.7 yards per attempt on just 52 carries before a broken arm ended his season. Both he and Breida played exceptionally well while healthy. Their injuries

don’t hurt their grades. They got injured because football is violent and running backs take a bigger beating than any other

position.

All three should be healthy to start next season. Which means the 49ers will have an electric trio of running backs, plus three-time Pro Bowl fullback Kyle Juszczyk.

The 49ers’ top-three receivers from 2017 all struggled while playing through injuries in 2018.

Marquise Goodwin played through a quad contusion, a hamstring injury and a calf strain and got benched after missing five games. The 49ers’ quarterback rating when targeting him was 77.2.