Naomi Osaka's struggles continue with National Bank Open withdrawal

With the US Open a few weeks ago, Naomi Osaka is still trending downward.

The four-time Grand Slam champion retired from her first-round match at the National Bank Open against Estonia's Kaia Kanepi on Tuesday due to a back injury. Kanepi had been leading 7-6 (4), 3-0 at the time of Osaka's withdrawal.

From ESPN:

"I felt my back from the start of the match, and despite trying to push through it, I just wasn't able to today,'' Osaka said. "I'd like to pay credit to Kaia for playing well and want to wish her all the best for the rest of the tournament.''

Osaka followed that up with a more simple message on Twitter:

The withdrawal is just the latest bad result for Osaka in recent weeks, or months. Since falling to current world No. 1 Iga Swiatek in the final of the Miami Open in April, Osaka has competed in only four tournaments, with two wins across all of them. All losses have been in straight sets.

That included a first-round loss at the French Open, where she fell to Amanda Anisimova, and her most recent straight-sets loss to Coco Gauff at the Silicon Valley Classic. She missed a significant amount of time after that French Open loss with an Achilles injury, causing her to miss Wimbledon. Amid all that, she split with her longtime coach Wim Fissette in July.

Osaka entered the Canadian tournament ranked 39th in the world.

When Osaka competes again is unclear for now, as it obviously depends on the severity of her back injury. The US Open is scheduled to begin on Aug. 29.