The San Francisco 49ers dropped their preseason opener against the Tennessee Titans 17-13 at Nissan Stadium on Saturday night.

It was as preseason as a preseason game gets. Virtually no starters played for the 49ers, but that opened the door for some of the reserves deeper on the roster to get some run. That means there is plenty to learn and take away from the contest.

Here's our notebook from each quarter:

First quarter

- Jordan Mason is the starting running back with Brandon Allen at quarterback. Mason is a dawg. He should be firmly in the mix for the backup RB job.

- Chris Hubbard is the starting left tackle. Jaylon Moore was working with the first team at that spot in camp, but he's under the weather according to the 49ers TV broadcast. Nick Zakelj is playing center. No Jake Brendel for the preseason opener.

- One of the things that could hold Mason back is his pass-catching. He got open on a second-and-9 on the first drive, but he couldn't pull down a high throw from Allen. It would've been a tough grab, but it's one he needs to have.

- Good find by Allen to hit Ronnie Bell for a first down on a third-and-9. Bell is finding his way as a pass catcher.

- Lot of two-tight end sets for the 49ers to start the game. It's Brayden Willis and Eric Saubert. They're the frontrunners to grab roster spots at TE.

- Touchdown on the 49ers' opening drive by Mason. He plowed in from four yards out with a little help from rookie right guard Dominick Puni. He Mason had 34 yards on six carries to open the game. Good series from Allen, too. He went 3-for-5 with 45 yards.

- The 49ers' first dynamic kickoff is a disaster. It went back for 63 yards. They missed several tackles on the play. Not good for a unit the 49ers invested heavily in this offseason.

- Good tackle by Ji'Ayir Brown on a toss to the left. He flew in from the free safety spot to stop running back Tyjae Spears for four yards. Those are good instincts from the second-year safety.

- Missed tackle by Dee Winters on a third-down throw short of the sticks. His miss allowed the Titans to get a first down.

- Redemption for Winters. He flew in and smacked quarterback Will Levis on a scramble to stop him short of the end zone on a third down. Ambry Thomas was whistled for holding in the end zone to negate the stop.

- Titans TD on the next play. Levis kept it himself on a sneak to score and tie the game.

- Undrafted rookie RB Cody Schrader was the second RB in the game. Mason was done after one drive.

- It might be hard to keep Chris Conley off the roster.

- Part of the reason it's hard to evaluate players in the preseason. Schrader took a toss left with Willis playing fullback as his lead blocker. Willis got obliterated and Schrader was dropped for a loss of two. There wasn't much the RB could do in that spot.

- Whew. What a play by Winters to fly in for a tackle-for-loss.

End of first quarter: 49ers 7, Titans 7

Second quarter

- Oof. Winters and LB Curtis Robinson got caught up in the wash on a short Titans touchdown run. Brown also whiffed a tackle on the play. It's 14-7, Titans.

- Drop from WR Tay Martin on a deep shot. Good throw from Allen. Flat out drop from Martin. That won't help his long odds of making the team.

- Good couple plays for CB Rock Ya-Sin. He defended a fade in the red zone to WR Calvin Ridley in the first quarter. He came up with a pass breakup in the second quarter as well.

- Rookie safety Malik Mustapha fell down while turning the corner on a blitz, and then got out of position on a corner route by a Titans TE.

- The 49ers pass coverage is a miss. Lots of blown coverages are leaving Titans pass catchers wide open. Expecting this to get cleaned up once starters are in and game planning begins.

- Another drop on a deep ball by Allen. This time Bell couldn't reel it in. Two good deep shots by the QB though.

- Really nice catch and run by WR Frank Darby on a dart from Allen. It went for 33 yards and got the 49ers out from the shadow of their own goal post.

- Rookie CB Renardo Green started the game at outside corner, but he moved inside on the Titans final drive of the first half.

- Yikes. Thomas whiffed a tackle on a third-and-10 screen that went for 36 yards before Robinson tracked down the RB. This hasn't been Ambry Thomas's best game.

End of second quarter: Titans 14, 49ers 7

Third quarter

- Good special teams tackle by Mustapha. Nice preseason debut for him.

- Really nice stop by Renardo Green on a throw into the flat. He chased down the receiver and dropped him short of the first-down marker after it looked like there would be an easy first down.

- On the next play, Green comes up with a fumble recover. Terrific showing for the rookie second-round pick.

- Joshua Dobbs is in at quarterback for the second half.

- Nice run by Schrader on first down after the fumble recovery. It was negated by a holding flag on Bell.

- The Titans get a free rusher at Dobbs who had his third-down pass batted down at the line. It looked like Schrader missed a blocking assignment.

- Matt Breida entered the game in the third quarter! Good to see Breida!

- TE Jake Tonges has a couple catches late in the third quarter. The second one was contested right at the sticks. He had to lay out to his right because the throw was a little off line. Nice catch either way.

End of third quarter: Titans 14, 49ers 7

Fourth quarter

- Another sack for defensive lineman Kalia Davis. He cleaned it up after LB Zeke Turner whiffed on a blitz.

- A fumble for Breida won't help his chances to sneak onto the roster.

- Whew, sweet throw on the run by Dobbs to hit Trent Taylor on a third-and-15. Dobbs got out to his left, kept his eyes downfield, set his feet and fired a strike to Taylor in the middle of the field. Nice play.

- Nice open-field stop by rookie LB Tatum Bethune on QB Malik Willis who got outside the pocket on a third-and-7.

- Dobbs sacked trying to extend a fourth-and-5 play. Tough for him behind a not awesome version of the 49ers' offensive line.

- Tracy Walker is having a heck of a game here late in the fourth quarter. He and Bethune both flew in for run stops to force a punt after the Dobbs sack on fourth down.

- Dobbs' final heave to the end zone is intercepted. Ball game over.

Final score

Titans 17, 49ers 13

This article originally appeared on Niners Wire: Notes and observations from 49ers preseason-opening loss to Titans