World number six James Blake called on the ATP Tour to change the rules at round-robin tournaments after a bizarre 24 hours when he went out of the Las Vegas Open, was reinstated and then eliminated again.

"If some good can come out of it, the revamping or destruction of the round-robin system, then that is something," Blake told reporters on Friday.

"It seriously needs to be looked at. We're going to run into situations every single week."

The American made his initial exit when Juan Martin del Potro retired during their round-robin match on Thursday.

Blake, leading 6-1, 3-1, needed to beat the Argentine with the loss of no more than five games to reach the quarter-finals.

But, under the rules, del Potro's withdrawal meant he had only completed one match, knocking him out of a three-way tie with Blake and Russian Evgeny Korolev in Group 1.

Since Korolev had beaten Blake in their round-robin match, the Russian advanced.

The ATP then reinstated Blake, saying it was a commonsense decision because the rule had not been properly explained, only to reverse its U-turn on Friday morning.

Under its own rules, the sport's governing body cannot overrule the ATP supervisor on such matters.

"After hearing all the reasons...I completely understand the rule," said Blake. "Evgeny deserves to be in the quarter-finals.

RULES FLAW

"The only thing is that a possible flaw in the rules has been exposed in this round-robin format."

Blake questioned the amount of control a player had in the situation del Potro found himself in.

"Once (he) was down 6-1 3-1 he could have lost a few more games and allowed me to go through or he could have retired and let Evgeny go through," said Blake.

"To put that kind of control in a player's hands is something that needs to be looked at."

Korolev thought the right decision was reached.

"It's a really difficult situation," he said. "I was a little angry but you have to understand the situation.

"James is a nice guy and I hope he's not angry with me. The thing is you cannot change the rules in the middle of a tournament."

Korolev said many players were against the round-robin format.

"I am actually glad this happened because a lot of players do not agree with the round-robin system," said the Russian.

The 19-year-old said he barely had any sleep after going to bed at 0300 but still managed to beat American Sam Querrey 6-4 6-4 to reach his first ATP semi-final.

"I was happy to play but I was also thinking how James would feel," said Korolev. "I felt a little guilty."