Lalkovic will stay with the Saddlers to the end of the season.
"I am delighted that Chelsea have allowed Milan to continue his development with us," said Saddlers' boss, Dean Smith. "He is getting better each week and has a hunger to learn and improve.
"Thankfully Chelsea see this as the right place for him to be able to do that and I look forward to continuing to work with him and help him develop, whilst at the same time, he plays his part in maintaining our challenge at the right end of the table during the battles which lie ahead."
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