Outside of Pro Bowl safety Eric Reid, last year's star rookie, Brock was the most significant contributor of any 2013 defensive back still on the current roster. Former starting cornerbacks Tarell Brown and Carlos Rogers are now out of the picture, finally leaving Brock at the No. 1 slot.
At the helm of a critical role in an overhauled defense, there may be no player with more pressure to perform in 2014.
Beyond Brock, the 49ers' cornerback depth chart is stocked with uncertainty. Projected starter Chris Culliver is working back from a knee injury on the opposite side, while top backups include underachieving newcomer Chris Cook with rookies Jimmie Ward and Dontae Johnson.
Leading this unseasoned group would be a challenge for any player, but rising to a challenge is nothing new to Brock.
As noted by Jeff Deeney of Pro Football Focus, Brock's rise to the NFL was far from typical. Stops at junior college, University of Minnesota and Belhaven University all preceded making the 49ers as an undrafted free agent in 2010.
This package from WAPT News in Mississippi further details the corner's rise from a small-school prospect to the starting lineup:
However, Brock is much more than simply a feel-good story about overcoming the odds. After cracking the rotation in Week 4 last season, Brock made the highlight reel with two interceptions against the Texans in the following game.
According to Deeney, Brock's sustained play earned him an overall grade of plus-8.1 from Pro Football Focus in 2014, good for ninth among qualifying cornerbacks.
Brock did not officially enter the starting lineup until Week 11, but he never looked back after seizing his opportunity. Deeney further boasted Brock's play with a 55.4 percent catch rate and just two missed tackles on the entire season, per Pro Football Focus.
Past the gaudy numbers, however, questions still remain about Brock and his teammates in the new-look defensive backfield.
Cornerback is the "diciest position on the team" according to Matt Barrows of The Sacramento Bee, as Brock and Culliver have just 13 career starts between them entering the season. While Brock's 2013 season was spectacular by all accounts, a limited sample size is a genuine cause for concern.
While coach Jim Harbaugh singled out Brock as having "a great camp again" in 2014 (per Austin Pentis of 49ers.com), defensive coordinator Vic Fangio expressed more caution. During a minicamp press conference, Fangio offered the following on Brock and the secondary, according to David Fucillo of Niners Nation:
I feel good about the guys that are here. Tramaine hasn’t been a full season starter, but he certainly played a lot of football for us last year. ... Anytime you lose two corners of Rogers and Brown, guys that have basically played every play here for three years...somebody’s got to step up and replace them. And we think we’ve got a group here that we can get those guys from that group. But, only time will tell.
Career highs in interceptions (five), passes defended (15) and total tackles (37) show that Brock was on the right path to stardom in 2013. With the rest of the cornerback depth chart in flux, the burden will be on Brock to repeat this trend for another successful season.
A retooled offense will only take this team so far if the pass defense falls apart, and Brock holds a great deal of responsibility in that regard.
Should Brock rise to the challenge, the 49ers will at least have solidarity on one side of the defense. If he falters, the team will be left with a rotation of uncertainty behind a front seven with questions of its own (i.e., linebackers NaVorro Bowman and Aldon Smith).
For their part, the 49ers have already expressed their confidence in Brock with a four-year contract extension in the middle of last season. Now it's up to Brock to simply do what he does best.
Exceed the expectations, time and time again.
All statistics and accolades according to Pro Football Reference, unless otherwise attributed. Tom Smeaton is a Featured Columnist for Bleacher Report and can be found on Twitter by following @ByTomSmeaton.