Mystery and intrigue are part of what make the NFL go.
Every year, there are players with various questions who could have a major impact on their teams' upcoming season.
With that said, here are 10 AFC North mysteries even Sherlock Holmes would struggle to solve in 2010:
2009 stats: 14 games (13 starts), 78 tackles, seven sacks
Why: Let's first give credit where credit is due: Timmons flashed more ability over the past few years than a majority of the players listed below. But his up-and-down 2009 season -- his first as a full-time starter -- raised a few questions. Does Timmons fit at middle linebacker, which is not his natural position? Considering his tremendous athleticism, why did Timmons struggle at times in pass coverage? Also, the decision to bring back veteran inside linebacker Larry Foote, who started ahead of Timmons in 2007 and 2008 before leaving as a free agent, certainly adds some intrigue.
Mystery rating (scale of 1 to 10): 6.5
2009 stats: 14 games (four starts), 35 tackles, one sack
Why: Webb's mystery revolves around youth and injury. The Ravens feel Webb has the potential to be their starting cornerback next season. The former third-round pick played well opposite Domonique Foxworth for a brief stint before suffering a torn ACL in December. Now there are questions about whether Webb will be ready for training camp or even the start of the regular season. Does Webb have enough experience? Can he be the same player, or will it take another year to shake off the injury? These are all questions Webb has to answer next season.
Mystery rating: 7.0
8. Paul Kruger, DE/LB, Ravens
2009 stats: Nine games (one start), 11 tackles, one interception
Why: Many were surprised when the Ravens drafted defensive end/linebacker hybrid Paul Kruger in the second round last year. Baltimore already had a stud hybrid in Terrell Suggs, and the team later gave him a large contract extension. Kruger took even more heat when he barely saw the field during the first half of last season. Kruger often was inactive because he didn't contribute on special teams, which made the situation look worse. But Kruger did show a couple of flashes last season, particularly in Baltimore's home win over Pittsburgh. With the recent losses of defensive linemen Dwan Edwards and Justin Bannan in free agency, Kruger will be asked to step up in 2010.
Mystery rating: 7.7
2009 stats: 11 games (one start), seven catches, 106 yards
Why: Robiskie had the label as one of the most NFL-ready players in last year's draft. It was a major reason Cleveland took Robiskie in the second round. But Robiskie suffered through the same growing pains as other young receivers. An uneventful training camp and preseason left Robiskie without a role, and he didn't see much playing time until late in the regular season. Perhaps Robiskie wasn't ready or he didn't fit Cleveland's system. Either way, the Browns need help at receiver and Robiskie has a lot of catching up to do in his second season.
Mystery rating: 8.0
6. Donte' Stallworth, WR, Ravens
2009 stats: Did not play
Why: Stallworth hasn't played a down since the 2008 season. So no one knows what to expect from the veteran receiver in 2010. A DUI manslaughter case led to jail time and a year-long suspension from the NFL. But Stallworth impressed the Ravens with a strong workout, and the team believes he can add much-needed speed to Baltimore's offense. With Anquan Boldin and Derrick Mason in as the starters, there's not a lot of pressure on Stallworth to produce right away. If he gives Baltimore anything in terms of stretching the field, the Ravens will be in great shape offensively.
Mystery rating: 8.4
5. Matt Jones, WR, Bengals
2009 stats: Did not play
Why: Jones also was out of football until the Bengals gave him a call with hopes of improving their passing game. This offseason Cincinnati added Jones and Antonio Bryant and they probably will acquire a tight end in the draft to give quarterback Carson Palmer more options. Although it's a cheap and low-risk move by Cincinnati, reportedly the Bengals were not impressed with Jones' workout and signed him anyway. But the good news is the season doesn't start until September.
Mystery rating: 8.5
4. Andre Smith, OT, Bengals
2009 stats: Six games, one start
Why: The Bengals still do not have a firm grasp on what they have in last year's No. 6 overall pick. After agreeing to pay Smith a maximum of $42 million, Cincinnati cannot afford to wait another year with him on the sideline. Smith's rookie year could not have gone any worse. It started with a contract dispute that caused the right tackle to miss all of training camp. Then a foot injury sidelined him for most of the season. He got his feet wet toward the end of 2009, but additional offseason surgery is an early hurdle Smith has to overcome this year.
Mystery rating: 8.8
3. Limas Sweed, WR, Steelers
2009 stats: Nine games, one reception, five yards
Why: Sweed's inability to make big plays is literally a mystery to the Steelers. He was a playmaker at the University of Texas and displayed the same athleticism to get open in the pros. But there is something about catching the football and finishing the play that has plagued Sweed the past two seasons. The Steelers made it clear they're tired of waiting for the third-year receiver by signing free-agent veteran receivers Antwaan Randle El and Arnaz Battle. Perhaps Sweed needs a change of scenery to start over and clear his head.
Mystery rating: 9.0
2. Jerome Simpson, WR, Bengals
2009 stats: Two games, zero receptions
Why: Ignore the lip service the Bengals' coaching staff provides publicly about their faith in Simpson. Instead, look at its actions. Cincinnati signed two receivers (Laveranues Coles and Bryant) to four-year, $28 million contracts in back-to-back seasons. That clearly shows the team's lack of patience and confidence that the light bulb will finally turn on for Simpson, who was a second-round pick in 2008. Entering his third season, this may be Simpson's last chance to show his ability with Cincinnati. Simpson could be cut in training camp if he fails to dramatically improve from his previous two seasons.
Mystery rating: 9.3
1. Jake Delhomme, QB, Browns
2009 stats: 2,015 yards, eight touchdowns, 18 interceptions, 59.4 passer rating
Why: Delhomme, 35, is the biggest mystery in the AFC North next season, because he may or may not be done as a quality, starting NFL quarterback. Delhomme certainly didn't look the part last season, when he threw a career-high 18 interceptions. He was later benched and released by the Carolina Panthers. Yet, the Browns believe Delhomme can lead their offense and paid him $7 million this year. Good move? Only time will tell. Is it a risky move? Absolutely.
Mystery rating: 10.0