Buttler has been sidelined since England's semi-final defeat to India at June's T20 World Cup. The injury, initially sustained in July while preparing for the Hundred, ruled him out of the tournament and has continued to hinder his return to competitive cricket. Lancashire Lightning coach Dale Benkenstein revealed to BBC that Buttler re-aggravated his calf injury during rehab, which has ruled him out of the side's upcoming T20 Blast quarter-final clash against Sussex Sharks on September 4. Buttler had been eager to make his comeback in time for this crucial fixture, but the latest setback has dashed those hopes. "We've had some bad news on his recovery...He had an injury he was recovering from, and he's sort of tweaked it again. He's not only just out of our T20s, but I think he's even struggling to make the international ones. He was very keen to play for us," Benkenstein said. Despite this, England remains optimistic about Buttler's availability for the upcoming T20I series against Australia, which begins on September 11. The team is not overly concerned about his fitness and is hopeful that he will recover in time to lead the side throughout Australia's eight-match white-ball tour.