INDIAN WELLS, California - Novak Djokovic's 22-match winning steak ended at the hands of an inspired Juan Martin del Potro, who beat the Serbian star 4-6 6-4 6-4 to reach the Indian Wells Masters final.
Djokovic had not lost a match since falling to Sam Querrey at the Paris Masters on October 31.
His 17 wins this year included a run to a fourth Australian Open title and a triumph in Dubai.
In the final, Argentine seventh seed del Potro will face 11-time grand slam champion Rafael Nadal.
Nadal earlier on Saturday beat Tomas Berdych 6-4 7-5 in his semi-final.