West Ham midfielder Manuel Lanzini could be out of action for around a month after limping off during the 2-0 win over Liverpool, according to Hammers joint-chairman David Gold.
The Argentinian, just back in the side following a thigh injury, had impressed against the Reds at Upton Park, hitting the post before being forced off late in the first half.
Gold confirmed in a post on Twitter the player would undergo further tests to determine the extent of the problem, but said the 22-year-old could be out of action for up to six weeks.
Gold said: "We will know more about Manuel's injury after the scan on Monday but it could be 4/6 weeks. He was superb today."
In his post-match media conference, Hammers manager Slaven Bilic said he hopes the playmaker, signed on loan from Al-Jazira, will not be absent for an extended spell.
"They have told me a little bit and I will hear more tomorrow. It is not big. It is the same, it is not the hamstring or the muscle, it is some kind of abductor and the tendon. I hope it is going to be like they have said now, just a little bit (of time out)," he said.
"If you watch the games again, the impact he made against Southampton and the way he orchestrated today with 22 players on the pitch, but with him bossing the game, (you can see) what he means to us."