Somerset's Craig Kieswetter broke his nose and fractured a cheekbone after he was struck by a ball on day one of the Championship match with Northants.
Kieswetter retired hurt with Somerset on 143-4, after a delivery came through his helmet visor and he was taken to hospital for tests.
The club have confirmed he will take no further part in the match.
"Craig is in very safe and capable hands at this time," said director of cricket Dave Nosworthy.
"These freak cricketing accidents happen from time to time and I am confident with the right care that he will come through this setback."
South Africa-born wicketkeeper-batsman Kieswetter has played for England in one-day and Twenty20 internationals.