Perhaps currently the Lions' biggest weakness, Detroit still has much to do to improve this position. The Lions lost two tackles in the offseason, both of which were most likely going to get significant playing time. Cory Redding was traded with Detroit's fifth round pick for linebacker Julian Peterson, and Shaun Cody was lost to free agency (Houston). While both players had their fair share of weaknesses, their departures have left a gaping hole in the middle of Detroit's defensive line.
Mayhew targeted this problem when he signed 12-year veteran Grady Jackson. Jackson comes from Atlanta where he predominantly played on running downs given his physicality (listed at 6'2", 345). But Jackson does not have enough left in him to be an every-down player, and aside from him, the Lions do not have a lot of talent. Chuck Darby was brought in last year and failed to make a big impact. The team also drafted two defensive tackles to add depth, but Landon Cohen and Andre Fluellen have yet to break onto the scene. Though it is too early to completely give up on these players, they've shown very little to instill confidence (11 tackles between the two rookies last year). Last year, the Lions were completely vulnerable in the middle of the line. They ranked last in the league in rush defense on runs in the middle and last in total rush defense (by yards).
B.J Raji provides an opportunity for the Lions to make an immediate upgrade. The defensive tackle out of Boston College has an impressive mix of size (6'1", 323) and speed. Watch the first 30 seconds of his highlight reel (then watch the rest), and you'll see the chaos that he creates in the backfield. However, there are some issues with Raji. There have been rumors that he failed a drug test at the combine, although his people vehemently deny it. But rumors aside, his character issues are well documented. Raji missed the 2007 season because was academically ineligible and also failed a drug test during his time with Boston College. Many also consider Raji too much of a reach to pick first overall. However, given Detroit's complete lack of talent at the position, they will be making a huge mistake if they don't even consider picking Raji first overall. Ideally, the Lions would be able to trade down three or four spots and take Raji, but trading out of the first pick is looking very unlikely. Personally, I would not be opposed to taking Raji at one. If the Lions do not land Raji, expect them to take at least one defensive tackle early on in the draft.
Given how horrible Detroit's defense was last year, it seems strange to say that they are actually mediocre at the defensive end position, but that appears to be the case. Surprisingly, the Lions ranked 9th in adjusted sack rate, last year. This means, on passing plays only, the Lions sacked the quarterback 9th most often (by percentage). This core is lead by impressive veteran DeWayne White and rising stud Cliff Avril. White joined the Lions in 2007 and had 6.5 sacks and four forced turnovers in both 2007 and 2008. He has proven that he can be a reliable difference-maker who will give you his best every Sunday. Avril, entering his second year, also had 6.5 sacks last year and has already made an impression on defensive coordinator Gunther Cunningham. Cunningham said of Avril, "I liked Avril when he came out. I thought he was a special athlete with his ability to rush the passer." But what remains to be seen is if either of these players can handle the all-important right defensive end position. Going against the offense's best lineman is going to be a challenge for both players. But Avril earned the RDE position halfway through the season last year and had success (earning The Sporting News all-rookie team honors). Aside from these two players, the Lions have little depth. Jared DeVries can come off the bench and be an adequate replacement, but youngster Ikaika Alama-Francis is running out of time to prove his worth. The Lions could use a little more depth at this position, but the starting jobs appear to be taken.