April 30 (Reuters) - Belgium's ⁠Alexander Blockx continued his breakthrough run at the ⁠Madrid Open on Thursday, upsetting defending champion Casper ‌Ruud 6-4 6-4 to reach the semi-finals of a Masters 1000 event for the first time in his career.

Blockx had never ​won an ATP Tour-level match on ⁠clay before this month ⁠but he has thrived in Madrid, earlier knocking out third ⁠seed ‌Felix Auger-Aliassime en route to the last four.

Blockx wrapped up the victory in 96 ⁠minutes to become the fourth-lowest-ranked player to reach ​the semi-finals ‌in the tournament's history. The world number 69 ⁠showed few ​signs of nerves as he dismantled Ruud with aggressive baseline play and solid serving.

"I'm proud of how I've played ⁠these past couple of matches. I ​think the conditions suit me well here," Blockx, 21, said in his on-court interview.

"I feel like it's clay which ⁠is slow, so I have time to settle and hit my shots, go for my shots.

"At the same time, it's quite fast with the altitude and ​the heat sometimes. I think it's ⁠the perfect combination for me."

Blockx will next face either ​second seed and two-time champion ‌Alexander Zverev or 10th seed Flavio ​Cobolli, who meet later on Thursday.