that didn't bother Djokovic, he still showed up to beat the USA.
Then he'll just go play on clay and still beat Murray.
It did not bother him, no. Then again he has already achieved world no.1 status. Also your Djokovic example doesn't really work for you as he picked up an injury, who knows how that will affect him?
Also he was playing in the real Davis cup, GB are just trying to qualify.