As the 'Upon Further Review' series charges on, it's time to take a look at what went wrong for the Buffalo Bills' back half of the defensive front seven against the Tennessee Titans.

Were the linebackers as bad as they seemed to be on Sunday, or was the lack of run defense a result of shoddy play at the line of scrimmage?

Let's take a look at that, as well as the play of the running backs and tight ends.

Linebackers

Nick Barnett
Time on Field: 100% snaps played; 64 total
Stats: 9 tackles (5 solo), TFL
Plus/Minus: +1
Observations: On the field for the entire game, Nick Barnett enjoyed some success but also got caught on some big plays throughout the contest. His most glaring mistake occurred on the play that allowed Chris Johnson to go 83 yards untouched and in to the end zone. Barnett shot inside and had his outside shoulder trapped so he couldn't get himself back in the play. From there, it was a simple case of Johnson running as fast as he could. Barnett crept in within five yards of the line of scrimmage a couple of times and got bottled up by a blocker. However, Barnett showed no quite throughout the contest. The weakside linebacker worked his way through the game to challenge at the line of scrimmage at times, even getting a tackle for loss. It wasn't his best game nor his worst, but the problems with the run defense weren't completely on the veteran linebacker.
Grade: B-
Season GPA: 2.79

Kelvin Sheppard
Time on Field: 57.8% snaps played; 37 total
Stats: 9 tackles (5 solo)
Plus/Minus: -3
Observations: The former third-round pick had a poor showing against the Tennessee Titans. He couldn't disengage off blocks, over-pursued the ball carrier at times and even took a penalty early on in the contest. Sheppard's day was highlighted by his work when the Titans used Jamie Harper as their running back. However, Sheppard struggled to establish himself against the much more accomplished and impressive Chris Johnson.
Grade: C
Season GPA: 2.65

Nigel Bradham
Time on Field: 53.1% snaps played; 34 total
Stats: 5 tackles (4 solo)
Plus/Minus: -3
Observations: Sunday was a step back for the Bills' rookie strongside linebacker. Nigel Bradham enjoyed a pair of solid performances over his last two games, but was a part of the problem of the team not being able to stop the run against Tennessee. On separate plays, Bradham failed to shoot the gap to stop a big play, struggled to disengage from a blocker and took the wrong angle on a run play. Late in the game, though, Bradham did have a nice screen breakup. He's still young, but he has seen better games.
Grade: C
Season GPA: 2.65

Bryan Scott
Time on Field: 46.9% snaps played; 30 total
Stats: 7 tackles (5 solo)
Plus/Minus: +2
Observations: Late in the game is when Bryan Scott was truly noticeable. He had a nice pass breakup on Jared Cook, and also tackled the tight end on a key 3rd-and-10. Early on in the game, however, Scott really didn't do too much to stand out for either good or bad reasons.
Grade: B-
Season GPA: 2.73

Running Backs

Fred Jackson
Time on Field: 60.7% snaps played; 37 total
Stats: 9 carries, 71 yards, 8 receptions, 49 yards, TD
Plus/Minus: +5
Observations: At least for one week, it looked like Fred Jackson was fully healthy (or looked really, really close). Jackson was breaking tackles and using his hard cuts that have made him such a fan favorite for his physical style of carries. Jackson was able to avoid arm tackles left and right and that really played in to his strongest showing of the season. His only negative play came on a drop when a pass was thrown to him in the flat.
Grade: A-
Season GPA: 3.13

C.J. Spiller
Time on Field: 47.5% snaps played; 29 total
Stats: 12 carries, 70 yards, 6 receptions, 32 yards
Plus/Minus: +4
Observations: Once again for C.J. Spiller, his speed and vision really stood out. All he needs is a little seam and he can break a play wide open. He even showed some toughness in bouncing off big hits to cut up field for a few more yards. His work in pass protection on the Ryan Fitzpatrick touchdown pass to Stevie Johnson helped give the quarterback enough time to make the throw. He gets a lower grade than Jackson, though, because Jackson had a higher yards per carry and a touchdown.
Grade: B+
Season GPA: 3.52

Corey McIntyre
Time on Field: 16.4% snaps played; 10 total
Stats: None
Plus/Minus: +1
Observations: Corey McIntyre has been used more as of late now that Fred Jackson is back and presumably healthy. McIntyre had a whopper of a block on a linebacker that led to a Jackson 7-yard run. Other than that, nothing else really stood out.
Grade: B-
Season GPA: 2.81

Tight Ends

Scott Chandler
Time on Field: 78.7% snaps played; 48 total
Stats: 2 receptions, 15 yards
Plus/Minus: +1
Observations: Most of the discernible plays for Scott Chandler happened in the blocking area more than the pass catching side of things. It's been like that now for two straight weeks, as Chandler was all but taken out of the game against Arizona. Once again, it was an up-and-down week for the tight end for blocking purposes. He missed a block on a screen play early on in the game, and later on failed to hold Kamerion Wimbley at bay, to which the defensive end plowed through and brought down C.J. Spiller. However, Chandler did seal off Akeem Ayers on a solid gain on the ground and made up for his earlier missed block on a screen by helping out Spiller in that respect. It's not for a lack of getting open, but Chandler has only three receptions in his last two games.
Grade: B-
Season GPA: 2.91

Lee Smith
Time on Field: 13.1% snaps played; 8 total
Stats: None
Plus/Minus: +4
Observations: This was the best performance of Lee Smith to date. He's shown the penchant for racking up penalties this season. However, Smith was amped up and it showed in his tenacity during run blocking. He was finishing blocks and helped clear the way for some solid gains on the ground. He neutralized Derrick Morgan (in run blocking) whenever he was matched up against him. It was a very good game for the second-year blocking specialist.
Grade: B+
Season GPA: 2.72

- Those that did not appear in the game on offense or defense were not graded.

- For obvious reasons, this is a report that highlights my findings and opinions from the individual games.

- The GPA's attached at the bottom are an overall grade of how I felt that player performed, basing it all on the play-by-play film review done throughout the week. B- is considered average on my scale, not C.

- Plus/minus scores and GPAs will be tracked as the season goes along. An individual game's GPA will be weighted with how many snaps that player has on the field in the contest when figuring out a season long average.

Twitter: @JoeBuscaglia