Mills has been cleared of any wrongdoing by the Football Association following the aerial collision which left Elder with a fractured eye socket and cheekbone, but the Millers skipper has been troubled by the extent of the injuries.
Robins told the Star: "It was as I expected, that Pablo would be cleared of any wrongdoing.
"But it was a horrible injury, Pablo was upset by the nature of it and I think he was a little bit subdued the other night (at Chester) because it had affected him mentally a bit.
"I spoke to him at half-time in that match and he was a bit better second half.
"All through he has been concerned how Nathan is going on and I would like to say once again that we wish him a full and speedy recovery."