The 49er’s pass defense was bad in 2018. Very bad. They gave up 35 touchdown passes and set the all-time NFL record for fewest interceptions, with 2. TWO. In 16 games.

PFF ranked them dead last among the 32 teams, rating defensive backs individually bad across the board. Richard Sherman had a rating of 68.9, and the eleven other Niners with 100 snaps or more in the secondary were all lower.

So what did John Lynch do? Nothing. He peeked at his poker hand, looked the other GMs in the eye, and said, “I like these cards. I’m staying pat.” And somehow, the Niners now have the best secondary in the NFL.

Technically, the Niners did add two defensive backs — free agent Jason Verrett and 6th round pick Tim Harris, two injury-bedeviled bargains — but they were discards. The pair managed just 14 regular season snaps combined before going on the injured reserve list. Harris didn’t get out of training camp, and Verrett looked bad in his brief action. So they’re not part of this turnaround, yet — though they offer a slim chance of returning in time for the playoffs.

Lynch’s ice-blooded gamble is all the more amazing when you consider who he decided to rely on:

Richard Sherman, a cornerback who was great with Seattle’s Legion of Boom (2012-2015). But he was never that fast even at his peak, and he entered last summer’s training camp at 31, a year removed from the Achilles tear that prompted Seattle to flat out cut him.

Akhello Witherspoon, who followed his brilliant rookie season with a sophomore slump, as quarterbacks hesitant to test Sherman tortured him. He seemed to lose confidence and was benched in the Arizona and Green Bay games as a result, before recovering a bit toward the end of the year.

Emmanuel Moseley, an undrafted free agent in 2018, was cut in training camp and signed to the practice squad. He was promoted to the roster on November 1st against Oakland and played just three snaps before suffering a season-ending shoulder injury.

Jimmie Ward, a talented DB shuffled back and forth from safety to CB, who ended 4 of his 5 NFL seasons early due to broken bones. Many fans wanted to ditch him on health grounds, or at least force him to drink more milk.

Jaquiski Tartt and K’Waun Williams, solid but unremarkable veterans at strong safety and nickel cornerback, respectively.

Three reserves who hadn’t shown much production (Marcell Harris, Tarvarius Moore, and DJ Reed).

That’s it — the talent that made Lynch confident enough to stand pat,

He even cut several of the backs on the roster — CB Greg Mabin and safeties Adrian Colbert, Antone Exum, Godwin Igwebuike and Tyvis Powell. (Exum was re-signed this week after Tartt broke a rib against the Ravens.)

How did that work out for him? It couldn’t be better. Sherman healed more fully from his Achilles tear and showed that old age and treachery beat youth and speed, at least for one more year.

Stephen Gilmore is the NFL’s consensus best cornerback, but Sherman is statistically almost identical to him. Neither has given up a touchdown, and they’ve played a nearly identical number of snaps (689 and 693, respectively) with very similar completions allowed (38 to 35).

Gilmore has four interceptions to Sherman’s 3, but he’s been targeted 74 times (to Sherman’s 58, a marker of respect). Gilmore has given up 386 total yards (to Sherman’s 297) and has worse averages for yards per completion (10.16 to 8.49), yards per target, and yards per snap (0.56, to Sherman’s 0.43).

Witherspoon regained his confidence and became a dominant shutdown corner. When Akhello got injured, Mosely just up and became an NFL stud for no apparent reason.

E-Man did have lots of top-level college experience playing for Tennessee, which was unusually competitive in the SEC during his four years there. They were ranked #22 in the nation his sophomore and junior years.

K’Waun and Jaquiski (you know which ones I mean) also became elite. Jimmie Ward stayed healthy (knock wood). Marcell Harris has played only 56 defensive snaps all year, but one of them killed a Ravens drive when he ripped the ball out of Lamar Jackson’s arms.

(By the way, it was not “Jackson’s first fumble of the season,” as some media reported. He put the ball on the ground twice against Seattle, and once each against Cleveland, Pittsburgh, and the Rams — all on running plays. But it was the first of his six fumbles that the Ravens didn’t recover.)

Put it all together, and they are simply the best passing defense in the NFL. Football Outsiders sets their passing DVOA at -45.0%, compared to -42.1% for the Patriots — and a mere -14.6% for third place Baltimore.

Granted, the GM and coach see a lot of things in practice that fans and reporters aren’t privy to. I also think Richard Sherman deserves a lot of credit for mentoring and inspiring the many young DBs on this team.

But the one crucial acquisition that John Lynch last summer was not a player at all. It was coach Joe Woods, the deeply experienced DB coach was served as the Bronco’s defensive coordinator the last two years, and worked with Kyle Shanahan in Tampa Bay.

He has gotten very little publicity this year, but when a passing defense goes literally from worst the first with the same players, you need to give most of the credit to the new DBs coach. But save some praise for the GM who had cuts to stand pat and pulled an inside straight flush.