John Isner beats del Potro in Miami Open semifinal

John Isner celebrates after defeating Juan Martin del Potro, of Argentina, 6-1, 7-6 (2) in a semifinal match at the Miami Open tennis tournament, Friday, March 30, 2018, in Key Biscayne, Fla. (Lynne Sladky/AP)

KEY BISCAYNE, Fla. — Towering John Isner moved one big step closer to the most prestigious title of his 14-year career.

Dominating with his serve and aggressive baseline strokes, the 6-foot-10 Isner beat a weary Juan Martin del Potro 6-1, 7-6 (2) in Friday’s semifinals at the Miami Open.

Isner ended a 15-match winning streak for del Potro, who won Indian Wells two weeks ago by beating Roger Federer in the final. The toll of so many matches showed, and Isner was the better player from start to finish.

He raced to a 3-0 lead, finished with 13 aces, never faced a deuce point on his serve and was at his best when closing out the victory.

Isner smacked consecutive aces to reach 6-all, and made all four first serves in the tiebreaker, including aces of 138 and 139 mph. He also hit two drop volleys for winners in the tiebreaker, with the second coming on match point.

Del Potro, seeded No. 5, was the fan favourite thanks to South Florida’s large Latin population, and a flag-waving, ole-singing, near-capacity crowd tried to inspire a rally from the Argentine after he quickly fell behind. But Isner held his own even in the occasional extended rally, and he repeatedly quieted the crowd with his big serves.

Seeded No. 14, Isner is 0-3 in ATP Masters 1000 finals. His opponent Sunday will be the winner of the other semifinal between No. 4-seeded Alexander Zverev of Germany and No. 16 Pablo Carreno Busta of Spain.

Isner is seeking to become the first American to win the Key Biscayne title since Andy Roddick in 2010.

American Sloane Stephens, the No. 13 seed and the reigning U.S. Open champion, will play No. 6 Jelena Ostapenko of Latvia on Saturday for the final women’s title on Key Biscayne. The tournament will move 18 miles north next year to the Miami Dolphins’ stadium.

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