SANTA CLARA -- Eric Mangini wants his safeties to be aggressive. But there were times Sunday when first-time starter Jaquiski Tartt may have been a bit too hawkish.
An example: Rams running back Todd Gurley's 71-yard touchdown run. On the play, Tartt took off toward the line of scrimmage but advanced too far to adjust to Gurley, who hit no resistance at the line of scrimmage and was barreling in the opposite direction.
The objective on the play, Mangini said, was for Tartt and fellow safety Eric Reid to form a funnel and limit where Gurley could run. With Tartt in his review mirror, Gurley instead had the run of the field.
"You want to hurry but you don’t want to rush, Mangini said. "It’s making sure you take the time to see exactly how the play is unfolding and then have the fit that you need to have or be where you’re supposed to be in the passing game. There were times where he was hurrying, and there were times where he was too quick to the ball."
Still, it was an overall promising game for the 49ers' second-round draft pick. Tartt finished tied for second on the team with six tackles and forced a Rams fumble, the first of the season for the 49ers defense.
Mangini noted that it's easy to coach aggressive players to play with more caution. The opposite is far more difficult.
"If they don’t bite when they’re puppies, they don’t bite when they are older," he said. "But you can coach it the other way and get them to tempo it down. And there was some of that in the game, which was all in the right spirit of it. But you’ll see growth with him too as we move through the season.”
Minus one 66-yard catch and run by Rams receiver Tavon Austin, the 49ers did a good job in pass defense Sunday. St. Louis had 191 passing yards.
The next challenge, however, is a bit more daunting.
Falcons quarterback Matt Ryan is s first in the NFC in passing yards while Atlanta receiver Julio Jones is first in the NFL with 892 receiving yards. Veteran quarterbacks tend to look at the opposing safeties as the "tell" for what the defense will do on a specific play, and Tartt knows Ryan's eyes will be on him.
"I'm the rookie," he said. "He's been in the league a long time, and of course he's going to look at me to try to get a pre-snap read off me. I've got to do a great job of disguising."
Fine tuning -- The Rams-49ers game had 25 accepted penalties but only two fines. Rams linebacker Akeem Ayers was levied a $8,681 fine for unnecessary roughness while Ahmad Brooks was docked $17,363 for a horse collar tackle on one of two plays on which he was called for a face mask.
Not fined: Rams Cody Davis, who may have given Reggie Bush an out-of-bounds shove on the play on which Bush hurt his knee, and Anquan Boldin who shoved a Rams player even though Boldin was not playing due to a hamstring injury.