Uruguay’s Cuevas denied the 29-year-old Spanish left-hander his 100th career ATP final by outlasting 14-time Grand Slam champion Nadal over three hours and 28 minutes on his beyond red clay surface.
Cuevas, who fired the last of his 11 aces on the final point of the match, will play for the title on Sunday against Argentina’s 71st-ranked Guido Pella, who eliminated Austrian fifth seed Dominic Thiem 6-1, 6-4.
Nadal converted only two of 13 break-point chances and made 33 unforced errors against 32 winners while Cuevas, 30, blasted 48 winners against 37 unforced errors.
In the first tie-breaker, Nadal sent a forehand long and double faulted to squander his first two set points but followed with a forehand crosscourt winner before Cuevas sent a backhand wide to end the 77-minute opening set.
Cuevas grabbed a 5-3 edge in the second set but netted a forehand to surrender a break in the ninth game that led to the second tie-breaker. Cuevas captured the last three points on two forehand winners and a netted Nadal forehand to force a third set.
Nadal surrendered an early break in the final set and could not answer, Cuevas winning all 17 of his first serve points in the third set, seven of them aces.
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