Haye has previously said he intends to fight both brothers before retiring
WBA heavyweight champion David Haye could still face either of the Klitschkos this summer, the brothers' manager Bernd Boente has revealed.
After protracted negotiations, Haye and IBF and WBO champion Wladimir have agreed to a fight on 25 June or 2 July.
But if an abdominal injury were to rule Wladimir out his brother, WBC champion Vitali, could face Haye in his stead.
Boente added that the fight would not necessarily occur in Germany, though he ruled out Britain as a venue.
Boente, who added that the United States would not host the fight, stressed that the contract signed did not specify which of the Ukrainian siblings Haye would meet.
It has been widely assumed that Haye will face Wladimir in a German football stadium on either 25 June or 2 July, but Boente said: "In the talks, David was not rejecting Vitali any more, he was very flexible.
"Knock on wood it's not the case, but should anything happen injury-wise [to Wladimir], as long as it is not three days before the fight or whatever, then Vitali could be the opponent."
However for that option to be feasible Vitali would first have to win his fight against Odlanier Solis on March 19.
Whichever brother Haye faces, the fight is likely to be in Germany although Boente added that there were "two or three" options in other countries.
"It is not 100% going to be in Germany," he said.
If everything goes the right way from a revenue point we are all winners
"The stadiums in Dortmund, Gelsenkirchen and Kaiserslautern are available and very interested in staging it.
"There are two or three other options that we are exploring in other countries."
Haye has already seen fights against both brothers fall through and the 30-year-old has vowed to retire before his next birthday in October.
And Boente confirmed that the signed contract was a simple one-fight deal, adding: "If everything goes the right way from a revenue point we are all winners."