It’s still unclear precisely why the trade of defensive tackle Shaun Rogers from the Lions to the Bengals fell through on Friday.  One thing we know is that the league office refused to approve it.  But the league office won’t say what the problem was.

“We consider it club business for the clubs to discuss or not as they deem appropriate,” NFL spokesman Greg Aiello told us via e-mail.  “Teams discuss many trades that are not completed, consulting with our office during the process if necessary.”

But neither the Lions nor the Bengals have said much about why the trade was rejected.  More accurately, they haven’t said much that makes much sense.

Per the Dayton Daily News, Cincy coach Marvin Lewis explained that the rejection of the deal arose from “how Detroit had to count cap figures, and the timing [of it].  It’s more in legality terms of league [rules] and how Detroit tried to execute it, and when they did it, it was too late, and so they [the league] just disallowed it.”

Ironically, the Bengals took a backhanded swipe at their own web site when discussing media reports that the deal had gone through.  Said Bengals P.R. director Jack Brennan:  “You’re aware that even though this [trade] was incorrectly reported from other sources in the media, we never made an announcement on it.  Obviously, for every trade that occurs, there are numerous discussions between teams that don’t lead to an actual trade.”

The cached version of the story regarding the trade from Bengals.com, which we discovered via our rudimentary Googling skills, makes it clear the team-owned Internet publication was reporting the transaction as a done deal.

So what happened?  Our semi-educated guess is that the Lions incorrectly thought that, if they consummated the deal before 12:01 a.m. on Saturday, March 1, responsibility for Rogers’ $1 million roster bonus due as of March 1 would be shifted to his new team.  But the league office (again, we’re speculating here) might have told the Lions that if Rogers is still on the roster when the clock strikes 4:00 p.m. on February 29, Rogers can’t be traded in the eight hours before business opens the following day.

In other words, if the trade wasn’t finalized by 4:00 p.m. on February 29, then it couldn’t have been finalized before Rogers earned the $1 million roster bonus at 12:01 a.m. EST on March 1.

If we’re right on this, it means that the Bengals would have given up a third-round pick, a fifth-round pick, and $1 million in cash and cap space order to get Rogers.  Once the $1 million became irrevocably the responsibility of the Lions, a trade went down without the new team having to pay the bonus.

Maybe that’s why the Lions got cornerback Leigh Bodden instead of a fifth-round pick from the Browns.  Cleveland was able to get Rogers without paying the extra $1 million — and without having to carry that amount on its salary cap in 2008.

Again, if we’re right, we can understand why the Lions and the Bengals are being vague about the reason for the failure of the trade.  It essentially means that neither front office understood a basic concept such as the moment at which responsibility for a roster bonus cannot be avoided.  And candor in this regard likely would have led to the same kind of embarrassment that dogged the Vikings after bumbling their first-round picks in two consecutive drafts.