This was built up to be a grueling game. The 49ers and Titans are both physically imposing, run-first teams, clashing on a short week.

That physicality was evident on Thursday, but make no mistake, this game was close only because of Jimmy Garoppolo’s failures. And because of him, San Francisco lost a game it should have won, falling in Tennessee 20-17.

San Francisco’s first drives on either side of the ball were near perfect. Kyle Shanahan dialed up a stunning, legitimately flawless opener.

It was a nine-play, 75-yard opening salvo that quieted the Nashville crowd. Touches were found to Deebo Samuel, Brandon Aiyuk, George Kittle and Jeff Wilson Jr., who punched home a one-yard touchdown run to cap it off.

The defense responded by stuffing a screen pass on its first play, then responded to a first down with a Samson Ebukam sack. Tennessee then tried to run on third-and-15, and failed miserably.

The ensuing drive provided a prime opportunity for the 49ers to take control of the game. Garoppolo ensured that didn’t happen.

With a similarly dominant recipe, San Francisco chugged the ball down to the Tennessee eight-yard line. With George Kittle losing his leverage, Garoppolo lost his mind, throwing an interception in the end zone, his first red zone pick since 2019.

The defense stood up Tennessee yet again, and Garoppolo followed it up with arguably his worst miss of the game.

It seems that once a game, Kyle Juszczyk finds himself wide open down the sideline, and nearly every time, Garoppolo makes Juszczyk go superhuman to try and catch it.

That was the case on Thursday, as Garoppolo overthrew Juszczyk in absurd fashion.

After a bizarre Trent Williams face mask penalty following a defensive offsides, that drive ended in a field goal.

Again, the defense held the Titans, and Garoppolo was nearly picked off again over the middle of the field by linebacker Rashan Evans.

Kyle Shanahan responded with a very clear indictment of his mistrust in his quarterback to conclude that half. Despite knowing that Tennessee would receive the second-half kick, he opted to sit on the ball.

After a completion to JaMycal Hasty got the 49ers into a third-and-2 situation, and with two timeouts remaining, Garoppolo ended the quarter with a quarterback sneak. Shanahan opted not to use either timeout.

The 49ers entered halftime up 10-0. Without the two Garoppolo gaffes, it would have been 21-0.

Immediately, the momentum shifted in the second half as A.J. Brown began to have his way with the 49ers’ secondary and their insistence on deploying soft zone coverage.

Tennessee opened the second half with a field goal. Garoppolo made sure they immediately got the ball back, overthrowing Deebo Samuel badly.

From there, it was the A.J. Brown show.

At one point, Ambry Thomas was big-brothered by Brown so bad that Brown just jumped in front of him and effectively caught the ball uncontested.

In the second half, the 49ers’ coverage completely fell apart. While the defensive line sacked Tannehill three times and Nick Bosa had a near sack that drew a holding call, the pressure wasn’t getting home as consistently as it had in recent weeks.

Without that sustained pressure, the coverage struggled to hold up, and Tennessee was ruthlessly effective on third downs, going 9-for-16 (including a third-down to set up the final field goal).

There were definite questions to be asked of DeMeco Ryans’ approach, though there is the objective fact that Ambry Thomas and Josh Norman are poor corners at this stage of their careers.

That consistency from Tennessee, in tandem with Garoppolo’s struggles — which continued with him overthrowing Aiyuk on a key fourth down — allowed them to turn the 49ers’ 10-0 lead into a 17-10 Titans lead.

There was nearly a San Francisco comeback. Deebo Samuel put his body on the line with a stunning play to get the 49ers in position to tie the game, courtesy of an Aiyuk touchdown.

But the 49ers’ mistakes did them in, and Tennessee drove back down for a game-winning 44-yard field goal by Randy Bullock.

San Francisco is now 1-5 this season in games with a negative turnover differential (-2 tonight), and per Josh Dubow of the Associated Press, lost their first-ever game with a 10-point halftime lead.

There is definite credit to be given to Ryan Tannehill and A.J. Brown, and for the Titans’ defense taking away George Kittle and the middle of the field, but this one was on Garoppolo’s turnovers and wasted opportunities.