James Blake went out of the Las Vegas Open on Friday after governing body the ATP admitted an earlier decison to reinstate him had been incorrect.
Blake was initially told he had missed out on the quarter-finals
The American finished tied with Juan Del Potro and Evgeny Korolev in the round-robin stage after Del Potro retired with Blake leading 6-1 3-1.
The ATP said Blake should qualify as he was on course when Del Potro retired.
But 24 hours later, ATP chief Etienne de Villiers admitted: "Clearly, I was wrong to intervene."
I regret that I got involved, that I overruled a supervisor, and I regret this storm in a teacup
Etienne de Villiers,
ATP chief executive
Blake had needed to win his final match in straight sets with the loss of no more than five games to secure a quarter-final place, and the suggestion was that Del Potro's retirment had denied him that chance.
De Villiers stepped in, saying: "James was within just a few games of winning this match comfortably to advance."
However, 24 hours later the ATP chief executive said: "I was contacted late at night my time and did not fully understand the issues being discussed and I made a judgment call on what seemed fair.
"However, I understand that judgment calls are not part of the rule book and I must abide by the rules, as must everybody else in the circumstance.
"I apologise to James for giving false hope and to Evgeny for the confusion. I regret that I got involved, that I overruled a supervisor, and I regret this storm in a teacup."
Following a similar situation in Buenos Aires, the round-robin format that was introduced at the turn of the year faces an uncertain future.
"Discussions with ATP Board members and other parties have already started and the future of round robin play has now been put on the agenda for the ATP Board meeting, starting in Miami on 22 March," said De Villiers.