I don't believe anyone has mentioned this yet so let me be the first... Henderson plays "X" receiver (backing up Colston) while Copper plays "Z" receiver (backing up Horn) in Payton's offense. These positions are quite different, in terms of both pass routes and run block assignments, kind of like split end vs. flanker. So, all this wondering and questioning why Copper is the #2 WR ahead of Henderson is misguided, I think. The real question should be why doesn't Colston move to the "Z" spot while Horn is out, thereby allowing Henderson (or Copper) to play the "X". Although, I'm sure Henderson's shoulder injury had something to do with it, not to mention the fact that Colston is a rookie afterall and why mess with karma?
When Copper first joined the team, if you recall, Payton said that he wanted him to start out as "X" and was basically 3rd on the depth chart at that spot (BTW, Jones and Moore backed up Horn at "Z" when the season started). Obviously, with Moore being "demoted" to PS (due to Beerman's return), and with Jones' lack of production, Copper was asked to learn the "Z" as well, and has done a decent job filling in for Horn. However, once Horn comes back, Copper will be back on the bench and assume his #4 WR role. That's because when the Saints go 3-receiver set, Henderson enters as the #3 WR (split end on the line) and Colston, usually, moves to the slot (off the line).
Next year? look for Colston to take over Horn's "Z" spot and Henderson, Copper, etc. to fight it out for "X". Of course, I'd like to see that happen now, with Joe moving to the slot as the #3 WR. If Copper can play the "Z" then surely Colston can too, this year, right? And I would think that Colston-Henderson tandem would be every bit as effective as Horn-Stallworth ever was... imho :)
Just Testing