Walcott has been left out of Fabio Capello's England squad for the forthcoming finals in South Africa after suffering a series of injuries and loss of form.
Former England coach Eriksson caused a huge stir four years ago when he selected the then 17-year-old Walcott - at that stage without a single Premier League game to his name - in his 23-man squad for the finals in Germany, although he did not feature at all in the tournament.
A hat-trick in a World Cup qualifier against Croatia in September 2008 only enhanced his chances of playing in South Africa, but Capello opted to leave him out of this year's squad.
Asked whether he was surprised at the slow pace of Walcott's development, Eriksson, who will coach the Ivory Coast in the finals, told BBC Radio Five Live: "Yes I'm surprised because four years ago he was the golden boy, or (showed that he) can be the golden boy.
"Maybe the expectation on him was too big, I don't know. The only person that can speak about that is Wenger. Four years ago I thought he could be a great player - and he still can be of course."