Lambert says they can become his first-choice central defensive pairing.
"Our defensive effort was terrific at Selhurst Park," said Lambert.
"Okore and Clark worked very well together, Alan Hutton was outstanding too, and with (Brad) Guzan and (Aly) Cissokho formed a strong unit there.
"For Okore it's his third game in quick succession, and he's been out for more than a year.
"And I think Ciaran Clark certainly: the two of them have certainly stepped up their game.
"That's the aim of football, to have selection conundrums, and those two are going to give me that when others return.
"You've got to push a mate to get into a side, and at the minute these two lads are holding their own."
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