Each Friday, Eight in the Box will highlight a list of eight players, teams or moments and their impact on the 2013 season.
The 2013 rookie class did not enter the league with as much hype as a lot of its counterparts -- just wait until 2014 to really see the difference. Despite their lesser billing entering the league, plenty of first-year players, both drafted and undrafted, made their marks over the season's first half.
Here's a look at eight of the more surprising stars to emerge:
8. Jordan Mills, T, Bears: Has it been pretty at all times for Mills? Not even close. But the fifth-rounder out of Louisiana Tech has played every snap on offense this season and has coughed up just one sack. (Sure, he's permitted a whopping, team-high 30 hurries, but the end results have not been disastrous.) Paired with fellow rookie Kyle Long on the right side of Chicago's line, Mills has given the Bears hope for a steady future up front.
7. Marlon Brown, WR, Ravens: New England's Kenbrell Thompkins has received most of the undrafted receiver attention this season, but we'd be remiss to overlook Brown. The 6-foot-5 Georgia product has 21 receptions and three touchdowns for a Baltimore offense that has struggled mightily in its attempt to find playmakers.
That 21-catch number is second among the Ravens' receivers, behind only Torrey Smith, and it's fourth on the team trailing Smith, Ray Rice and TE Dallas Clark. Brown has lost snaps to Jacoby Jones of late, but don't be surprised if he pushes his way past the veteran again.
6. Joseph Fauria, TE, Lions: The NFL's rookie touchdowns leader (non-quarterback division), Fauria thrust himself into the limelight with a highlight-reel effort -- both as a football player and a dancer -- against the Browns, and he has found the end zone five times in all. Not bad for an undrafted player. Fauria's blocking has left plenty to be desired, and it's why the Lions have used him only in spot duty. But Detroit might have at least one more loss on its record without Fauria.
5. Joplo Bartu, LB, Falcons: Perhaps the most anonymous of the unheralded rookie stars, Bartu leapt from Texas State to free agency to a key role in the Falcons' linebacking corps. He enters Week 9 with 34 tackles and 2.5 sacks, the sack total behind only Osi Umenyiora and Corey Peters on his own team.
Atlanta has a second undrafted linebacker picking up minutes at linebacker, too: Paul Worrilow, out of Delaware. Worrilow has 17 tackles so far, following up on a stunningly productive preseason.
4. Zac Stacy, RB, Rams: A fifth-round pick, Stacy entered a crowded Rams running back situation alongside 2012 draft choices Isaiah Pead and Daryl Richardson. He's slowly taken over as the No. 1 guy in that backfield, with team-leading stats in carries (76) and yards rushing (348). Those 76 attempts match the combined number for Richardson and Pead -- the latter has run the ball just seven times this year, mainly due to a suspension.
The 2013 class of running backs, despite being shut out of the draft's first round, actually has delivered a very solid year. Green Bay's Eddie Lacy and Cincinnati's Gio Bernard (who scored this ridiculous touchdown Thursday night) have established themselves as legit starters, while players like Le'Veon Bell and Andre Ellington are slowly leaving their imprint.
3. Jordan Reed, TE, Redskins: The Redskins knew they had found a potential playmaker at pick No. 85 in this year's draft. They'd be lying if they told anyone they anticipated Reed being this impressive this early. Through eight weeks of the regular season, the ex-Florida Gator leads all rookies in receptions, with 34. He's been such a key part of the Washington offense, in fact, that the team reportedly tried to trade veteran Fred Davis before the recent deadline.
2. Marcus Cooper, CB, Chiefs: Cooper was drafted in the seventh round this past April ... by the 49ers. He failed to crack San Francisco's roster, so Kansas City claimed him off waivers. All he's done there is pick off two passes, break up six and rank as Pro Football Focus' fourth-best cornerback in the league this season. Cooper has been a godsend in the Chiefs' secondary, picking up the slack when Brandon Flowers was out of the lineup. The 49ers have to be kicking themselves for letting him get away.
1. Tyrann Mathieu, CB, Cardinals: That Mathieu had top-end talent was no secret. There were major questions for the 2013 third-round pick, however, regarding Mathieu's ability to translate his game to the NFL level after sitting out all of 2012. He has put on quite a show to this point.
Mathieu recently was named the NFL's Defensive Rookie of the Month for October, a month he capped by recording his second career interception against Matt Ryan in Week 8. The Cardinals have kept Mathieu on the field in just about all situation, and he has repaid that trust by flashing a remarkable combination of skills and understanding of the game. In addition to hounding receivers, Mathieu has proven again to be a dangerous pass-rusher -- he has one sack and seven QB hurries in 2013.BURKE & FARRAR: The Playbook: Previewing Bears-Packers, Saints-Jets, more Week 9 games