Tennis pundit Jon Wertheim has issued a lengthy apology after appearing to mock Barbora Krejcikova's appearance in a clip which was accidentally broadcast.

Journalist and author Wertheim was preparing for an appearance on the Tennis Channel during the WTA Finals earlier this week when, as he dialed in via Zoom, cameras captured him showing a side profile and saying: "What do you think I am? Barbora Krejcikova? Look at the forehead."

The clip circulated online with tennis fans calling on Wertheim to apologise. Krejcikova herself released an angry statement on Sunday, calling his behaviour 'unprofessional' and accusing him of lacking 'respect'. "I want to see [tennis] represented in a way that honors the commitment we make to compete at this level," she added.

Wertheim has now broken his silence on the fiasco, and the American insists he holds himself accountable. "During a Tennis Channel studio show on Friday, I made some deeply regrettable comments off-air," he wrote on X. "I acknowledge them. I apologize for them. I reached out immediately and apologized to the player."

He also added context to the clip, suggesting that his remarks came across particularly badly in isolation. Wertheim wrote: "What happened? I joined the show by Zoom. In rehearsal we were shown a graphic of a player who had just competed. It showed her at an angle that exaggerated her forehead.

"A few moments later, I was told to frame up my Zoom. I looked at the low camera angle and joked that it made my forehead resemble the photo of the player in question. Someone in the control room chimed in and I bantered back.

"Though this was a private rehearsal, this exchange inadvertently and without context, made it to live air. I realize: I am not the victim here. It was neither professional nor charitable nor reflective of the person I strive to be. I am accountable. I own this. I am sorry."

Krejcikova acquitted herself well at the WTA Finals, which she qualified for despite ranking outside the top-seven due to her Wimbledon triumph in the summer.

The Czech, 28, lost to Iga Swiatek in her opening match. But she came roaring back with straight-sets wins over Jessica Pegula and eventual champion Coco Gauff in the group stages, before coming up short against Qinwen Zheng in the semi-finals. Krejcikova took home just over £800,000 for her two round robin wins and participation fee.