Novak Djokovic competing in the "unique" Davis Cup so soon after winning the US Open comes as an honour for tournament director Feliciano Lopez.
Serbia's Djokovic defeated Daniil Medvedev to equal Margaret Court's record of 24 grand slam triumphs after a straight-sets victory earlier in September.
At 36 years and 111 days, Djokovic became the oldest winner of the men's singles title at the US Open, as well as winning three majors in a year for the fourth time in his career.
That saw him surpass Roger Federer – who won three grand slams in a year on three occasions – but unlike the Swiss star, Djokovic has shown no signs of slowing down.
The 36-year-old was straight back into action just five days later, overcoming Alejandro Davidovich to help Serbia into the Davis Cup quarter-finals with victory over Spain.
Former Spanish tennis player and now tournament director Lopez hailed the endeavours of Djokovic for appearing in Valencia in such a short period after victory in the United States.
"As you can imagine having Novak here in Valencia this week is such an honour first of all," Lopez told Stats Perform.
"I personally appreciate a lot what he's done by coming here after winning the US Open because I know how tough it is to win a slam and then three or four days after put yourself in a position to compete again at the highest level.
"I don't think I can thank him enough that he's here ready to compete, ready to represent his country.
"I have to take my hat off and say thank you and wish him all the best for the rest of the week."
Djokovic has reiterated his commitment to helping Serbia to a second title in the men's Davis Cup, a tournament that Lopez believes is different to any other.
"I think the fact that you're representing your country is one of the things that I wanted to say [about what makes it special] because tennis is an individual sport where you normally play for yourself," he added.
"Whenever you have the chance to play for your team-mates, for your country and for a lot of people that you know, they put in a lot of efforts during that particular week to make everything happen.
"For me, it's the most special thing and unique."