Lakeside Hammers co-promoter Jon Cook has warned his misfiring riders they could be replaced.
The Hammers fell short at Peterborough on Thursday, losing 50-42 to suffer their fourth straight away defeat in the Elite League.
And with an 18-day break looming after Saturday's visit of King's Lynn, Cook could be making changes.
"We'll look at what's available and see if a change of face or two might make a difference," he told BBC Essex.
"We know there's not a wealth of riders out there.
"It seems to me these riders need to show they really want to be here a little bit more.
"At this moment in time it's just not good enough, is it?"
Cook's problems have been exasperated ahead of Friday's trip to Coventry.
Captain Lee Richardson has been told by the British Speedway Promoters' Association that he can not pull out of the British semi-final at Scunthorpe to ride against the Bees.
Stuart Robson is also in the semi-final, while Kyle Legault is representing Newport and Peter Ljung will still be recovering from a back injury.
The Hammers have called in former Coventry riders Rory Schlein and Ricky Wells as replacements.