Jesse Ryder has been ruled out of New Zealand's ICC World Twenty20 Super Eights match against Ireland at Trent Bridge on Thursday.
The batsman, 24, remained in London for further tests on a sore groin muscle when his team-mates travelled up to Nottingham.
He has been troubled by various groin injuries in recent times and the Black Caps' medical team are trying to establish if the latest problem is linked.
New Zealand team manager Dave Currie said: "Jesse is continuing to suffer serious discomfort and has been admitted to hospital for observation and further tests, which we hope will provide a clearer picture of his condition."
Ryder scored a quickfire 31 in New Zealand's victory over Scotland last Saturday but missed Tuesday's one-run loss to South Africa.