Trio expected back for Palace/Helenius trains this week
Villa face the Eagles on April 12 at Selhurst Park.
Delph missed out against Fulham with a sore leg, Agbonlahor had a bug which he failed to shake off while El Ahmadi was absent with a thigh strain.
Despite all three being unavailable for the Whites encounter, Lambert believes strongly that the key trio will be fit to face Tony Pulis's men.
He said: "There will be a good chance the three of them will be back next week.
"It's been a big chunk of our squad. If you go through them - Jores has virtually missed the whole season, Libor has missed half a season, Christian is out for six months or so.
"There's been major, major injuries. It's not like they have been strains. These have been big injuries.
"We had Fabian missing against Fulham and Gabby too and Karim, who has been playing really well of late. That's a big, big chunk.
"These are lads who have played a lot of the season."
Lambert also said that striker Nicklas Helenius is set to train this week after being sidelined with a troublesome thigh strain.
He admits tall forward Helenius - a summer signing from AaB - has been terribly unlucky with injuries this season.
The 22-year-old has only made six substitute appearances and scored one goal - in the FA Cup third round clash against Sheffield United.
Lambert added: "Nicklas has had a thigh strain - an abductor strain.
"He might begin training at the start of the week.
"He has had little injuries which have kept him out. But hopefully he will train this week."
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