The 27-year-old Yorkshireman has yet to score for United in 28 appearances since he arrived at St James's Park in a £6m move from Manchester United in the close season.
Before yesterday's defeat by Blackburn Rovers, Keegan told the Evening Chronicle: "If it was about honesty, determination and hard work, then Alan Smith would have scored three or four goals for us now.
"But I think he's only really had one chance, and that was a half-chance. We haven't created enough for him.
"It would be nice for him to score. I'd love to see him get a goal because he deserves to from his endeavour, honesty and work rate.
"You can't get enough Alan Smiths around your club. They're good people to have. They come in every day, train properly, set good standards and have a bit of character. I like him a lot."
His lack of goals, and the fact that he never had a settled position under Allardyce, has meant that Smith has yet to win over the fans - but Keegan is convinced he will.
The United boss added: "The thing is, he'll probably start scoring a goal or two on the back of his endeavour and then they'll love him.
"You'd love him to be a fans' favourite because he should be, but fans will see what they see."