In each of the four years from 2015 to 2018, the San Francisco 49ers failed to produce a .500 record and never eclipsed six wins in a season. There was an expectation that the offense would be vastly improved this year with the return of quarterback Jimmy Garoppolo from his torn ACL, but the defense still had question marks. It couldn’t get much worse than what it was so there was hope of marginal improvement on the defense, but no one expected the improvement they actually made.
After tying for 26th in EPA per play allowed in 2018, the 49ers jumped to second behind only the Patriots.