Davis Cup: Evaluating Clay Players at Indian Wells

There were 14 players in the Indian Wells men's singles main draw who played live rubbers on clay during the previous weekend's Davis Cup World Group Ties; 10 of these were seeded:

-13) Ferrer, 18) Robredo, 28) Lopez, Almagro (ESP)
-Chiudinelli (SUI)
-2) Djokovic, 29) Troicki, 30) Tipsarevic (SRB)
-15) Isner, 17) Querrey (USA)
-Sela (ISR)
-O.Rochus (BEL)
-14) Stepanek, 19) Berdych (CZE)

So the point of this post is to discover if playing on clay really affected performance on the hard court of IW.  I would say the evidence is a bit inconclusive and you cannot rush to the conclusion that players should skip Davis Cup to focus on Indian Wells.  These 14 players went a combined 19-14 in IW, but 2 of the losses were retirements (Almagro and Tipsarevic) and 3 more lost to other players in this list (Sela to Robredo, Querrey to Isner, and Stepanek to Sela).

Obviously Djokovic, Ferrer, and Stepanek were major disappointments but given their last few tournaments is that really surprising?  I don't think you can say for sure that it was because of DC clay.  This group also produced 2 quarterfinalists (Robredo and Berdych) and several others lost to top-tier players (Roddick beat Robredo, Soderling beat Lopez, Nadal beat Isner, etc, and even Djokovic lost to the eventual champion).

Interestingly enough, the three players performing poorly were the highest seeded of this group, so perhaps the surface change affects top-tier players more than middle-road players?  I argue that based on 2010 DC/IW, a player should not skip DC to avoid a surface change since several of the players still performed well at IW.