Great Britain's Emma Raducanu was forced to retire from her Guadalajara Open first-round match with Australia's Daria Saville due to a hip injury.
The US Open champion - taking part in her first match since the Australian Open - endured a marathon encounter with her counterpart and took the first set 7-5 before going down 6-7 in the second after an intense tie-break.
Both players appeared to be struggling with the conditions in the WTA's longest match of the season, with Saville 4-3 up in the third set after three hours and 36 minutes.
Raducanu attempted to play on with her leg taped after taking a medical timeout in the dying embers, but the 19-year-old was ultimately forced to retire, with the WTA confirming that she had sustained a left hip injury.
The British number one took seven of her 19 chances to break Saville on the day but also posted nine double faults, and Saville will now take on the USA's Caroline Dolehide in round two.
