England claimed a 4-1 win over Montenegro which means victory over Poland will secure a place in Brazil as Group H winners.
"The result will give us a huge lift and it's good for confidence going into the final game," Gerrard said.
"But the message is that the job's half done. Poland are a very good team. They're going to come and do us no favours, like Montenegro, try to make it really difficult for us.
"It's important that we perform to the same level as on Friday night."
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