Southampton boss Ronald Koeman admits losing Morgan Schneiderlin for their clash with Arsenal is a big blow.
France midfielder Schneiderlin hobbled out of Saints' 3-0 Premier League defeat to Manchester City at half-time on Sunday.
"Morgan's not ready for Wednesday because he needs a scan on his adductor, in his right leg," said Koeman.
"Then we have to wait about the result of the scan.
"For sure he isn't available for this Wednesday, but he'll have scans to find out exactly what happened.
"It's too soon to know whether it's serious.
"It's not too soon to say he can't play on Wednesday, but how long he will be out I don't know."
