DE Ziggy Ansah (Round 1, 5th overall): -0.7
Thanks to a strong second half of the season, Ansah nearly dug his way out of the negatives. He finished with 8.0 sacks in 14 games (the most of any rookie this season), and he landed 30th in PFF's defensive end rankings. Considering he had a pretty rough three-game stretch toward the end of the first half of the season, that's not bad.
CB Darius Slay (Round 2, 36th overall): -7.0
Slay's playing time on defense was pretty sporadic during his rookie season, mainly because he was so inconsistent. In his first career game, he registered a -4.4 grade on PFF, and he actually had a total grade of -10.4 at one point. He put together his best game ever on Thanksgiving, but a knee injury kept him out for most of the rest of the season. Hopefully his play on Turkey Day will end up being a sign of things to come considering his overall rating on PFF put him 92nd at cornerback.
OG Larry Warford (Round 3, 65th overall): +22.8
Warford actually graded out as the Lions' top offensive player on PFF. Overall, he placed fourth among offensive guards on PFF and second among right guards. Considering it took him nearly all of training camp to truly take control of the starting right guard job, what he did during his rookie season is pretty amazing. The Lions definitely got a steal by landing Warford in the third round.
DE Devin Taylor (Round 4, 132nd overall): +0.5
Taylor had a pretty up and down season, as he seemingly always followed up a great performance with a bad one based on PFF's grades. I suppose that's what you should expect from a fourth-round pick, but Taylor did have 2.5 sacks and 2 forced fumbles in 14 games. He should be a part of the Lions' rotation at defensive end for the foreseeable future.
P Sam Martin (Round 5, 165th overall): +30.7
As the kickoff specialist for most of the season and the full-time punter, Martin racked up a +30.7 rating as a rookie. He finished 18th among kickoff specialists on PFF and seventh among punters. At times he was too inconsistent, but he was a big upgrade for the Lions' special teams units, especially with his average of 47.2 yards on punts in 2013.
RB Theo Riddick (Round 6, 199th overall): +0.3
Riddick's playing time on offense was pretty limited during his rookie season. He carried the ball only 9 times for 25 yards and a touchdown, and he had only 4 catches for 26 yards.
Undrafted free agents
OT LaAdrian Waddle: +7.9
Waddle ended up making eight starts for the Lions as a rookie. He graded out as the 32nd overall offensive tackle on PFF, and he actually finished only 4.3 points behind Gosder Cherilus. With a full season of starting, Waddle could have finished ahead of Cherilus, and either way, Waddle looks to be the Lions' starting right tackle going forward. Not bad for an undrafted free agent.
TE Joseph Fauria: +6.2
Fauria finished 12th among tight ends on PFF despite receiving a pretty limited amount of playing time for most of the season. He ended up catching 18 passes for 207 yards and 7 touchdowns, and he was a beast for the Lions in the red zone. As his run blocking continues to improve, look for him to become a bigger part of the offense going forward.