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Jannik Sinner has said he "won't do it again" after breaking a rule at the start of his fourth-round match in Melbourne. The No. 2 seed is one of several players who have taken to the court wearing a screenless fitness tracker on his wrist - but he was told to remove it before facing Luciano Darderi on Monday.

Carlos Alcaraz and Aryna Sabalenka have also been asked to remove WHOOP devices from their wrists while competing at the Australian Open this fortnight. WHOOP's 3.0, 4.0, 5.0 and MG devices are approved player analysis technology devices under International Tennis Federation rules.

However, Tennis Australia has confirmed that the wearable trackers are still not permitted to be worn in Grand Slam matches. "Wearables are currently not permitted at Grand Slams. The Australian Open is involved in ongoing discussions on how this situation could change," they said in a statement.

"Some wearables provide athletes with an indication of internal load (measures like heart rate), which can give them a 360-degree view of the work they're doing and how their bodies' respond.

"In terms of other data provided to athletes and their teams at the AO, players can monitor key external load measures such as distance covered, changes of direction, high acceleration events and speed/spin of shots via Bolt 6."

After becoming the latest player to accidentally step on court while wearing one of the devices, Sinner has explained that he didn't know they were banned, but wanted to use the tracker for post-match analysis.

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