It looks like Jason B made a post already sort of covering this, but I called this when I heard the trade and friends were insisting that Asante was on the chopping block. Except I initially said that DRC would be the "Charles Woodson" type player in the defense, as he is the most mediocre of the three in coverage.... it's possible you will actually see both him and Aso rotating in the "Woodson" role.
Here's what the Eagles brass was considering after trading for Asomugha AND keeping Samuel:
As someone mentioned before, more plays were run last year out of the 3WR than 2WR sets.
Look at the NFC East alone:
NYG: Nicks, Manningham, Steve Smith (if healthy)-- all potential 1,000 yard receivers
Redskins: Moss, Stallworth, plus a stable of rookie wideouts (and Cooley)
Cowboys: Bryant, Austin, Witten, rooks
It's stacked with receiving talent. The best part is that I believe the vastly different playing styles of Asom and Samuel will complement each other, not clash. Asom can be assigned to bigger more physical receivers, Samuel can ALWAYS stay on the outside (shielding his lack of physicality) and get the space to do what he does better than ANYONE--including Revis and Asom-- namely, jump routes. Last year he picked off something like 7 out of 37 passes that were thrown his way, and you can expect more to come his way now that Asom is locking down the other side.
We have a straight lockdown guy, and then we have a guy that will more than make up for the couple times he gets beat by causing game-changing turnovers.
Teams are going to try to work the slots, but with DRC (or Aso) we shouldn't be a liability there. If you remove Samuel from the roster, there is literally no reliable 3rd cornerback, and teams will simply throw away from our starters every chance.
As for the linebackers, we'll probably only have 2 on the field more often than not. I think Jamar Cheney is going to have a breakout year; he has great instincts and a nose for the ball, and the rook mistakes he made last year were at least aggressive mistakes. Fokou is a serviceable starter. Akeem Jordan needs work but he's got speed and is already a great cover linebacker. We'll see about this Matthews kid and how the LBs play as a unit, but they have plenty of cover behind and in front of them.
People are saying to trade Aso for Patrick Willis.... nice idea, but the 49ers won't go for it. And there aren't any other LBs out there who are worth a straight-up trade for him (certainly not Tatupu), Ryan doesn't want a finesse guy like Samuel so it looks like my prediction was essentially correct in that they were fully prepared to keep all 3. Smart move, IMO.