Walcott started just 15 Premier League games last season, scoring five goals – a tally he has matched in his first eight appearances this term.
The 27-year-old should start the Gunners’ Champions League match against Ludogorets Razgrad on Wednesday.
“I was not ready to let him go. I always wanted to keep him,” said Wenger.
“I’ve felt that since he’s played with more freedom, maybe he lets his feelings come out a bit more and is less calculating: ‘Can I do that or can I not do that?’
“I think he has a less restricted attitude and that shows you that he is a completely different player.”
Arsenal face their Bulgarian opponents in back-to-back Champions League matches, knowing two wins could secure a place in the last 16.
They drew their opening Group A fixture against Paris St-German, before beating Basel 2-0.
Wenger’s side have won their past six games in all competitions and have not lost since a 4-3 defeat by Liverpool in their first match of the season.
Midfielder Francis Coquelin could start on Wednesday after returning from a knee injury in the 3-2 defeat of Swansea on Saturday.
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