Underdog Johnson through to ATP semi-final

American qualifier Steve Johnson is through to his first ATP Tour semi-final after an emphatic victory at the Delray Beach Open on Friday.

The 24-year-old, who eliminated top seed Tommy Haas in the second round, dominated sixth seeded Spaniard Feliciano Lopez to win their quarter-final 6-3, 6-2 in 73 minutes.

Johnson did not drop serve and broke Lopez three times.

"I stuck to the game plan and executed really well and in the end I was able to hold my nerves," he told reporters.

Johnson, ranked 142nd in the world, will meet 2012 champion Kevin Anderson in the semi-finals on Saturday.

Johnson might be the underdog against fourth seed Anderson, but will take confidence in the knowledge he beat the South African in Auckland in January.

Anderson advanced to the semi-finals with a 6-7(3), 6-3, 6-3 victory over Australian Marinko Matosevic.

"I just hung in there and finally got that breakthrough in the second set," said Anderson, who dropped serve once in the gusty conditions.

The other semi-final will pit Croatian Marin Cilic against American John Isner.

Seventh-seed Cilic advanced with a comfortable 6-3, 6-2 win over Russian Teymuraz Gabashvili.

"Good times are rolling," Cilic said after serving 12 aces. He also returned well, breaking Gabashvili five times.

It was Cilic's 11th straight-set victory in 13 matches since a second round exit at the Australian Open as he stayed on track for his third final in as many weeks.

He lost the final in Rotterdam last week, and won the week before on home soil in Zagreb.

Second seed Isner dropped the first set against Rhyne Williams, but recovered to beat his American compatriot 4-6, 6-3, 6-2.

The big-serving Isner pounded down 18 aces and only lost five of 45 points on his first serve.

Image: Steve Johnson

Photograph: Renee McKay/Getty Images