MADRID — Top-seeded Alexander Zverev got a warning from the umpire for taking a photo of a ball mark during the clay-court Madrid Open on Sunday after complaining about electronic line-calling.

During a clay court match in Madrid, Zverev pointed out the discrepancy between where the ball landed and Hawk-Eye’s call. During a clay court match in Madrid, Zverev pointed out the discrepancy ...

Despite multiple attempts, Zverev hardly closed the gap on No. 1 Jannik Sinner, who has been barred from tennis competition since February.