Isner ends Del Potro streak in Miami semi-finals
Juan Martin del Potro was unable to extend his winning streak to 16 matches as John Isner proved too strong in Miami.
John Isner ended Juan Martin del Potro's 15-match winning streak in straight sets as he eased into the Miami Open final.
Del Potro has been in outstanding form of late and has looked on course for a third successive title in south Florida having triumphed in Acapulco and Indian Wells.
However, a dominant performance from Isner put paid to those hopes, as the powerful American claimed a 6-1 7-6 (7-2) success.
Isner will now face the winner of the other semi-final between Pablo Carreno Busta and Alexander Zverev as he looks to win a first title since victory at the Atlanta Open in July last year, the 32-year-old having sealed his place as the top American player in the rankings by reaching the Miami showpiece.
Del Potro had won six of the previous nine meetings with Isner but lost the previous encounter in the quarter-finals of last year's Paris Masters.
On that occasion Isner needed three sets to defeat the Argentine, but he was in no mood to endure such a battle again and broke in Del Potro's first service game. A precise backhand down the line put him 40-15 ahead and the second break point was converted with a delicate touch at the net.
Isner duly consolidated the break to go 3-0 up and, though Del Potro carved out a battling hold of his own to get on the board, he could not reverse the tide.
The first set, in which Isner fired down 19 winners, was sealed in typical fashion with a brutal serve out wide, but the second proved far more attritional.
Neither player faced a break point until Del Potro staved off one in the ninth game, holding after Isner let his chance slip by firing a return into the net.
But Isner was ruthless in capitalising on his opportunity in the tie-break, winning the first three points and then, after Del Potro had held on each of his serves to trim the gap, rattling off a further four points in succession, victory secured by a sublime backhand volley at the net.