Sakho limped off during Sunday's 1-1 draw against West Brom with a thigh problem and early reports suggested he would be sidelined for three months.
An update on West Ham's website read: "(Diafra) suffered a significant injury to his left thigh
He underwent a scan on Wednesday and will see a specialist on Thursday, when we hope to learn more and put a more certain timeframe on his absence."
There is better news regarding Ecuador international Valencia, who has not featured since the 1-1 draw with Everton in early November
After being given permission to return to South America during his rehabilitation, the club are hopeful he will return to the field before the new year.
The club added: "We are pleased to report that Enner is progressing very well and, should his rehab continue to go as planned, he has a good chance to play before the end of the year
He is ahead of schedule and we have been very happy with his progress."
Source : PA
Source: PA