On the surface, this pair of linebackers seems like a good addition to the New Orleans Saints, a team that gave up 388 points last year to be ranked 25th in the NFL.
The problem is these big-name defenders don't play the right position. Even if Vilma and Morgan are healthy, their arrival does nothing to solve the Saints' biggest defensive weakness -- their porous secondary.
You don't have to look at advanced statistics like Football Outsiders' DVOA ratings (explained here) to know the Saints had the worst pass defense in the NFL last year. It was pretty obvious any time the Saints took the field.
New Orleans allowed 54 pass plays of 20 yards or longer, and most of those came with starting cornerback Jason David in coverage. David signed a four-year, $15.6 million contract to leave the Indianapolis Colts for New Orleans before the 2007 season, then went out and underperformed for most of the year.
David was solid in Indianapolis, primarily playing in a Tampa 2 zone, but was completely overmatched playing man-to-man for the Saints. According to the Football Outsiders game charting project, the average pass caught in a hole in zone coverage gained 11.6 yards. The average pass caught when David was in man coverage gained 13.2 yards -- meaning that in 2007, receivers did better against David than in empty space. David also finished last among all starting cornerbacks in our other defensive coverage stat, Success Rate (explained here).
The Saints' other starting cornerback, Mike McKenzie, was near the top of the league in Success Rate and a little above average in Yards per Pass. Unfortunately, McKenzie isn't going to be around much in 2008, because he tore his ACL in late December. Behind David and McKenzie are veteran Jason Craft, a reasonable nickel back who would be stretched as a starter, and Usama Young, a 2007 third-round pick from Kent State who spent most of his rookie season on special teams.
You can't blame the Saints for acquiring Vilma and Morgan instead of solving the problems at cornerback, because this wasn't a good year for free-agent cornerbacks. There was one star, Asante Samuel, and the Saints went after him. At one point, reports said the Saints were in the lead to sign Samuel, but in the end, he chose the Philadelphia Eagles.
After that, the drop-off was steep. The Saints signed hometown son Randall Gay, an LSU product who played nickel back for the New England Patriots last year. Gay could be a reasonable league-average starter. He was decent in both Success Rate and Yards per Pass in 2007. However, he is injury-prone, missing 24 games in 2005 and 2006, and he only fills the hole left by McKenzie's injury. He does nothing to solve David's struggles.
There also is no question the Saints had room for improvement at middle linebacker. The incumbent starter, Mark Simoneau, was available in trade two years ago because Philadelphia no longer thought he was starting quality. He hasn't done much in New Orleans to prove the Eagles wrong.
On most NFL defenses, the middle linebacker is either the top tackler or near the top. New Orleans was the only team last year on which the starting middle linebacker was not involved in at least 10 percent of all tackles. By comparison, Vilma led the league in tackles and was one of only two defenders (along with the San Diego Chargers' Donnie Edwards) to be involved in 20 percent of his team's defensive plays when he last played in a 4-3 scheme for the 2005 Jets.
The dilemma for New Orleans is that both Vilma and Morgan (who might move outside, replacing Scott Shanle as the starting weakside linebacker) play their best when tackling running backs, not covering wide receivers. That's not an area in which New Orleans needed much help. Although they couldn't stop opposing air attacks, DVOA rated the Saints as a top-10 run defense in 2007.
In fact, not only did New Orleans have a good run defense last year, but that run defense was strongest up the middle. The Saints ranked 10th in Adjusted Line Yards (explained here) on runs listed in the play-by-play as up the middle or behind a guard. However, they ranked 29th against runs around left end and 26th against runs around right end.
Now, there's no doubt a lot of those runs up the middle were stopped by Scott Fujita, not Simoneau. There's also a good argument that if Vilma's knee is healthy, his lateral speed will help him track down those runners coming around the ends. A healthy Morgan would be an upgrade on Shanle against those left-side runs. Still, it is hard to believe Vilma and Morgan can make the Saints' run defense much better than it was in 2007.
What about pass defense? Vilma and Morgan might help with covering the short pass, but neither Vilma (2.5 career sacks) nor Morgan (7.0 career sacks) is likely to spend much time rushing the quarterback. The Saints' defense sent the standard four pass-rushers 71 percent of the time last year, ranking them 24th in the NFL in frequency of blitzes.
Considering how a good pass rush can hide a bad secondary, the Saints' best defensive acquisition probably is a guy nobody is talking about, former Jacksonville Jaguars defensive end Bobby McCray. When injuries forced McCray into the starting lineup in 2006, he was strong in rushing the quarterback (10 sacks) and stopping the run (his average run tackle came after a gain of just 1 yard). However, he played a reduced role in 2007 and probably won't even start in New Orleans. Charles Grant and Will Smith still are atop the depth chart.
Given the available players this offseason, the Saints did what they could to improve their defense. Nonetheless, even if big-name acquisitions Vilma and Morgan are completely healthy, their effect on the Saints' defense probably won't be very significant.
Aaron Schatz is president of Football Outsiders Inc. and the lead author of Pro Football Prospectus 2007 and 2008.