The teenager has continued to spend as much time on the bench as on the pitch for the Gunners this season, despite signs that he is starting to fulfil the potential that prompted former national boss Sven-Goran Eriksson to take him to the 2006 World Cup.
But Bentley, whose career blossomed after he left north London permanently for Blackburn in January 2006, believes Walcott may have to "look elsewhere" before too long if he does not become a first-team regular.
"Sometimes you need football, you need games to become better, to put your skills out on the football pitch," Bentley told talkSPORT.
"If he is not getting the minutes at Arsenal, he's going to have to look elsewhere.
"Your career doesn't start and end at Arsenal. It can flourish somewhere else.
"At the end of the day you want to make a career for yourself.
You want to play football for a start and you want to make money as well.
"It's your job. If you want to make a career for yourself you can't afford to stay at a club where you might be 24 or 25 with 30 games under your belt."
Walcott, 18, has made 15 starts so far this season, already two more than in his debut campaign at the Emirates Stadium.
But if his chances continue to be limited given the weight of talent at the club, Bentley believes his experiences show the grass can be greener at a smaller club.
"It was hard to leave," he admitted. "I was there from when I was 12 years old and I had a lot of friends.
"It becomes like a home. It became comfortable. But I didn't want to accept not playing and thinking 'these players are better than me'. Every week I wanted a game."