Alexander Blockx, Madrid Open semifinalist, is ready for a bigger tennis court in every sense

MADRID — Jannik Sinner issued a warning Wednesday evening for everyone swept up by Rafael Jódar, the 19-year-old Spanish rocket ship who had just put him through two hours of stress at the Madrid Open.“Especially this tournament here, very young players are coming through,” he said. “We cannot forget also about Blockx, for example. He’s a bit under the radar, but he is an incredible player. Everyone is improving, so you need always to be in the present moment.”Less than 24 hours later, Blockx, first name Alexander, overpowered Casper Ruud, the defending champion and French Open finalist, 6-4, 6-4, and it wasn’t really that close.Blockx, a 6-foot-4 inch Belgian from Antwerp, is just 21. It’s hard to imagine many people had the world No. 69 making the semifinals on their draw ahead of the tournament. Blockx sure didn’t.“I never had too much confidence on clay in the last couple of years, but I think I cannot say that anymore with the results I’m doing,” Blockx said during an interview Thursday following his win.He had some good results on the ATP Challenger Tour earlier this year, winning two events and making the semis of another. All were on hard courts.He made