The Everton winger admitted on Wednesday that today’s fixture at the club where he spent 12 years from the age of 16 was the first he looked for after signing.
But his new manager insisted he must put on hold old friendships and make sure his Gunners mates are kicking themselves by the end of the afternoon.
Allardyce believes the support from both management and fans at Everton – something which was not always guaranteed at Arsenal – can prompt a late flowering of Walcott’s career.
“The more he plays like he did against Leicester the more the fans will appreciate him. And when you’re appreciated and supported and praised as a footballer it makes you feel good and more confident,” said Allardyce. “You can’t wait to get out there and upset other teams.
“He’s started well and we hope he continues that until the end of the season and for the next three or four seasons that he’s here.
“But the challenge for Theo in going to a new club, is showing everybody who you are and what you are as a footballer, and proving you live up to and better the reputation you have.”
Walcott’s man-of-the-match performance and two goals against the Foxes on Wednesday in only his second appearance for Everton ensured the price tag hung a little less heavily around his neck.
“I can’t say what Arsene [Wenger] thinks, but the opportunity to take a player with last season’s goals record and that quality [for £20m] wasn’t a big decision,” said Allardyce.
“A lot of things have been said about Theo – he hasn’t reached his full potential and all that – but I don’t know how you could say that after last season’s performance with 30-plus games and 19 goals.
“If he’d have been playing a lot this year he would have been happy to finish his career at Arsenal. But because he wasn’t getting his game time, he looked at his career and decided he had to leave.
“He chose us and hopefully he’ll be a big player for us.”