England batsman Alex Hales missed Nottinghamshire's opening Royal London Cup fixture for personal reasons, with the club saying "no timetable has been set for his return".
Hales was named in England's preliminary World Cup squad earlier this week and has been a consistently destructive force over the last four years - although he has recently found himself in the role of batting back-up, with Jason Roy and Jonny Bairstow establishing a partnership at the top of the order.
England's one-day players are set to meet up for a training camp next week, ahead of ODIs against Ireland and Pakistan. Their World Cup campaign starts on May 30 against South Africa.
"Alex Hales has made himself unavailable for selection for personal reasons and no timetable has been set for his return to action," Nottinghamshire said in a statement on their website.
Hales has a white-ball only contract at Notts, and has not played this season. His most recent cricket came at the Pakistan Super League in March.
Speaking earlier this month, Hales reflected on his role in the Bristol night out in 2017 that led to Ben Stokes' arrest, before looking forward to England's attempts to lift the World Cup for the first time.
"It's probably the most excited I've ever been in pre-season," he said. "It's arguably the biggest summer ever for England with a home World Cup. We are heading in as the bookies' favourite. Hopefully I can play the part in a memorable summer."
In Hales' absence, Notts had no trouble racking up the runs, totaling 417 for 7 before managing to hold off Lancashire in a match that saw 823 runs scored in total.