Needing to beat Argentine Juan Martin del Potro with the loss of no more than five games in order to advance, the defending champion and top seed was leading 6-1 3-1 when his opponent retired because of breathing problems, handing Blake a walkover.

Blake was denied a place in the last eight, however, as the rules state games won or lost in a walkover do not count.

His quarter-final place went to Evgeny Korolev on a head-to-head basis after the Russian beat Blake earlier in the competition.

Had Blake won a completed match with the loss of no more than five games, all three players would have been level on sets won and the American would have advanced due to a higher percentage of games won.

Korolev will meet Sam Querrey in the last eight after the American teenager beat his compatriot Paul Goldstein 6-4 1-6 6-4.