Alexander Zverev has taken to Instagram to share a photo he took in the middle of his third-round match at the Madrid Open. The No. 1 seed started debating an automatic line call during his clash with Alejandro Davidovich Fokina, disagreeing with the electronic system, which called one of his opponent's balls in. Zverev pleaded with the umpire to come onto the court and look at the mark but the official was not allowed to do so.

Instead, the German got his phone out of his bag and took a photo of the mark, delaying Davidovich Fokina's service motion. Zverev received a code violation warning for unsportsmanlike conduct as a result. But that didn't stop him from posting the picture after getting the win, and he's now planning to speak with ATP supervisors after claiming there was an issue with the technology.

Davidovich Fokina was serving to stay in the second set at 4-5 when Zverev started complaining about a ball mark. The Spaniard hit a forehand that appeared to just catch the line, with the electronic system ruling it in.

Automatic line calling is now used across the ATP Tour, including at clay-court events. In years past, umpires would come down from their chairs and manually look at a ball's mark on the court, deciding whether it was in or out.

Since the introduction of the automated system, they must go with the electronic call and cannot get out of their chairs. But Zverev wasn’t happy and marched over to umpire Mohamed Lahyani, asking him to come down to the court.

“Look at this mark. Please just come down, look at it. Don’t overrule it, please. Just come down, please. Just for me,” the world No. 2 asked as Lahyani told him he was not allowed to do so.

Zverev continued to plead with the umpire and claimed there was a “mistake” in the system. When he finally realised he was getting nowhere, he got his phone out and took a photo before Lahyani gave him a code violation.

The German continued playing and forced a decider, winning the second set in a tiebreak after losing the opener. He still wasn’t pleased, complaining about the system again during the changeover.

Zverev went on to win 2-6 7-6(3) 7-6(0), and the ball mark was still on his mind after the match. He took to his Instagram story to share the photo of the mark in question. “Just gonna leave this one here. This was called in. Interesting call,” the top seed wrote.

The 28-year-old is now planning to speak with the ATP after suggesting the system wasn't working during the match.

“I honestly think that there was a malfunction in the system in that moment. That's why I went to the umpire and I said, ‘Please, come down to have a look at this, I'm not crazy’. I can see what was happening,” he said.

“We'll see. It's going to be interesting to see what happens now, what kind of fine I will get, even though I'm right, you know. I hope I don't get a fine, because obviously, in my opinion, I'm completely in the right and I should not get fined for this.

“But, yeah, this was not normal. Normally the system is very reliable. Normally the system has been correct so far in my experience. But what happened today, I don't know.

“It's not the umpire's fault, because if he by rule cannot go down, he cannot go down. So it's not Mohamed's fault.

“But I will talk to the supervisors, I will talk to the ATP, because as I said, this is not normal. For a mistake to happen like this, yes, one or two millimetres I understand, but four, five centimetres is not normal.”

A two-time former champion in Madrid, Zverev is now through to the round of 16, where he faces either Francisco Cerundolo or Francisco Comesana. Cerundolo beat him here last year and the German will be out for revenge.