San Francisco 49ers: Things You Probably Didn't Notice in Week 1 Win

You know the San Francisco 49ers scored 21 points off first-half turnovers en route to a 28-17 win over the Dallas Cowboys. 

You know Vernon Davis caught two touchdown passes, Carlos Hyde had his first rushing touchdown and Frank Gore reached 10,000 rushing yards for his career. 

But what did you miss?

Here are five things you might not have noticed during San Francisco's Week 1 win. My apologies if you already knew about a slide or two, but my guess is you'll learn something new from at least one of these slides (and let me know in the comments below if you noticed all five). 

49ers' Base Run Defense Worse Than Nickel Run Defense

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The most troubling part of San Francisco's Week 1 victory was its run defense. 

Cowboys running back DeMarco Murray rushed for 118 yards on 22 carries. That was the most rushing yards the 49ers have allowed to one player since November of 2009, when Ryan Grant had 129 yards. 

What you may have missed was San Fran's base defense was actually worse than its nickel defense against the run. 

Murry had 74 yards on 12 carries when the 49ers were in their base 3-4, a 6.2-yard average. When Ian Williams was not on the field and an extra cornerback was in the game, the Niners allowed 44 yards on 10 carries, a 4.4-yard average.

If the Niners don't plug the rushing holes in the coming weeks, they'll get burned by Matt Forte, Andre Ellington, LeSean McCoy and Jamaal Charles—four of the most explosive running backs in the NFL. It's as simple as that. 

Colin Kaepernick's Improved Field Vision

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Trent Dilfer once said Colin Kaepernick was a "remedial passer once his first read is taken away" (h/t Bay Area Sports Guy). 

Dilfer is one of of many analysts who has publicly critiqued Kap's field vision. 

On Sunday, Kaepernick showed improvement in this area. 

On the 37-yard completion to Anquan Boldin in the first quarter, Kap started the play looking to his left for Michael Crabtree. Under pressure, he quickly looked to the other side of the field as Boldin was making his break on a deep post pattern. He took a hit as he threw a strike to No. 81.

On the ensuing play, Kap started out looking for Boldin again. He had to avoid an oncoming pass-rusher—which he did narrowly, I might add—and found Davis open for a 29-yard touchdown on the other side of the field. 

On San Francisco's next offensive play (after Eric Reid's interception return to the Dallas 2-yard line), Kap looked off a covered Bruce Miller in the flat and connected with Davis on a flag route for a touchdown.

Overall, Kap's eye placement was better. He was less obvious about where he was going with the ball on his throws. 

He'll face plenty of tougher defenses throughout the season that will more thoroughly test his field vision and pocket presence, but there's no doubt he can build off this performance. 

Ahmad Brooks Was SF's Worst Player

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It was a rough first quarter for Ahmad Brooks. The veteran outside linebacker was called for three penalties, and he missed a tackle on Lance Dunbar that allowed the backup running back to pick up six extra yards and a first down.

In the second quarter, Brooks shot the gap on a 3rd-and-1 run by DeMarco Murray, but the 2013 49ers Pro Bowler missed the tackle, allowing Murray to get a first down.  

After watching the game again, I thought Brooks' motor was lacking. On most run plays not to his side, he stood around instead of pursuing the ball-carrier. 

Evidently the 49ers coaches took notice, too, as he was on the bench for 22 defensive snaps. 

He salvaged his day (to a small extent) with a sack in the third quarter, but that wasn't enough to save his Pro Football Focus score from being the worst of his career, a minus-5.5 (subscription required).

Rookies Hold the Fort on Pass Defense

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Tramaine Brock and Chris Culliver both left the game in the first quarter with injuries. Brock returned late in the fourth quarter, while Culliver missed the rest of the game. For the majority of the last three quarters, the 49ers only played three cornerbacks: veteran Perrish Cox and rookies Dontae Johnson and Jimmie Ward.

They were up to the challenge.

Johnson was credited with two tackles and two pass breakups on 47 defensive snaps. Dallas completed three of seven attempts into his coverage for 28 yards. Overall, Johnson was the second-highest-rated 49ers defensive player by Pro Football Focus against Dallas (Justin Smith was first).

Jimmie Ward was only credited with one tackle. His best play—a near interception of a Tony Romo pass intended for Cole Beasley—was nullified by a rather soft illegal-contact penalty. 

All things considered, the 49ers have to be thrilled with the rookies' play. In 2013, Romo was ninth in the league with a 7.5 adjusted-passing-yards-per-attempt average. On Sunday, playing with two rookies in the secondary for most of three quarters, the 49ers held Romo and the Cowboys to 4.5 adjusted yards per pass attempt. 

Anquan Boldin's Perfect Day

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Eight targets, eight receptions. 

The Anquan Boldin-Colin Kaepernick connection is alive and well. 

Boldin had eight catches for 99 yards, which represented half of the 49ers' completions and 49 percent of their receiving yards. He was the only receiver in the NFL with a 100 percent catch percentage on at least eight targets. 

For his efforts, Boldin received the highest PFF wide receiver rating of the week. 

Just another day's work for the 12-year veteran.

Receiver stats via PFF. Joseph Akeley is a San Francisco 49ers featured columnist. Follow him on Twitter.