For each stat, I decided to measure each team's "Advantage" by subtracting the other team's overall NFL rank from their own. For example, St. Louis' Passing Offense ranks 27th in the NFL in Yards-per-Game, while Detroit's Pass Defense ranks 30th...therefore: Advantage: St. Louis + 3
Stats after the jump...
As their records and recent history would indicate, both teams are below average in most statistical categories, and near rock-bottom in a few.
St. Louis' biggest advantage might be on Special Teams (no surprise to Lions fans here). The Rams are punting the ball more than five yards farther per attempt than the Lions, and St. Louis' punt return YPA, kick return YPA, punt return defense, and kick return defense, each wins in a match-up against Detroit's punt return defense, kick return defense, punt return YPA, and kick return YPA, respectively.
Expect the Rams to consistently start with better field position and do a better job pinning the Lions back. The Lions do have the advantage in the field goal game though, with all-time leading Lions scorer Jason Hanson having made 90% (and we're all surprised it's not 100%, after he was 8-8 from 50+ yards last year), compared to only 66% this season for Rams kicker Josh Brown.
Measured in both Yards-per-Attempt and Yards-per-Game, St. Louis' overall offense is slightly better than Detroit's overall defense in every phase, and the same can be said for Detroit's offense against the Rams Defense.
The biggest advantage here would be held by the Rams and their rushing offense, being 10th in the league at 4.4 yards a carry, against a 28th-ranked Detroit rush D, allowing 4.6 YPC. Detroit is not, however, the pushovers that they were last year, especially with upgrades to the linebacking corps over the offseason, and having the bye week to heal up many of their injured defensive starters. Steven Jackson could have a very good game against Detroit's D, but I wouldn't be surprised to see the Lions step up and match up well against the Rams offense.
Detroit's rushing offense (23rd YPA, 21st YPG) is about even with St Louis' rushing defense (21st YPA, 27th YPG)
In the passing game, both teams' offenses holds a slight--very slight--advantage over the other team's defense. I expect an above average passing game from both teams.
I think there are some key overall game stats other than yardage that favor the Lions:
While neither team has impressed overall, especially after their most recent games (Detroit being shut out 26-0 against Green Bay, and St Louis getting blown out 42-6 by Indy), Detroit comes out just a little bit ahead in the all-important measure of points. Detroit is scoring 17.2 points per game (23rd), while St Louis is allowing 30.1 (30th). The Rams are scoring only 8.6 PPG (NFL worst) while the Lions are allowing 31.3 (31st). It's a battle of ugly and uglier so far this season, so anything could happen here.
One other area where Detroit holds a significant advantage is third-down conversion. The Lions are converting 40% on third down (16th in the NFL), while the Rams are dead last, giving up 51.6%. The Lions will need to push this advantage and stay on the field longer, especially since special teams performances indicate that they'll be starting with a longer field. Of course, everything the Lions can achieve on offense depends heavily on the health of Matthew Stafford and Calvin Johnson and whether those two can get on the field and produce.
The biggest advantages for Detroit are, most obviously, the much-needed bye week to heal up from injuries and home-field advantage, but I think this will be a close game that either team can win. Winnable games for both teams in these rebuilding seasons are rare, and they'll obviously both look to capitalize on a game against a beatable opponent.