Wenger will be relieved when the ink is dry on the deal, having helped develop Walcott from a raw talent when bringing him from Southampton seven years ago.
"I was scared at some stage, yes, that he could leave because it is like that with the experience I have in negotiations," Wenger said at this morning's press conference ahead of the Barclays Premier League game at Chelsea on Sunday.
"When things last too long, it is never a good sign.
"In that case, it took us some time to get where we want to get.
"It is still not finalised, but hopefully it will be done by this weekend.
"There is a possibility. My optimism is at 99 per cent now."