Sean Dyche revealed that summer signing Ben Gibson is facing another minor operation as the Clarets' defensive resources are stretched.
A 4-2 defeat at West Ham United made it 13 goals conceded in three games.
But former Middlesbrough centre-back Gibson is not yet in a position to challenge for a first-team place and Dyche also confirmed that James Tarkowski requires further attention to the groin problem that has dogged him so far this season.
"Ben is going to have a hernia operation and Tarky is going to see a specialist this week," said Dyche following the Clarets' loss at the London Stadium.
"Ben's kind of been right and not right, so we said 'if you're not right you've got to get it done.
"So they will look again and he will have some keyhole surgery. It shouldn't be a long one."
In addition to a second bout of surgery for Gibson, whose action so far since his arrival from Teesside has been restricted to the Europa League, and the concern over Tarkowski, Jack Cork and Phil Bardsley also missed the trip to London.
Cork's ankle injury sustained against Chelsea a week ago ended his ever-present league record for the Clarets stretching back to the start of last summer.
And with Bardsley picking up a knock to join Stephen Ward on the absent list, under-23s' defender Ali Koiki was part of squad at West Ham, who took the points thanks to late goals from Felipe Anderson and Javier Hernandez after Johann Berg Gudmundsson and substitute Chris Wood had twice levelled.
"The challenges we have got coming are that we thought we were nearly close to get eveyone fit, then this week Corky went down and Phil Bardsley went down.
"So just when we get there things change and therefore we have to put it all back to together again and keep working."