Both senior players have been linked with summer moves away.
But Charlotte FC coach Smith told the Daily Mail: “Villa don’t want to lose either of them and I don’t think they can.
“(Ollie) is another top lad that I keep in touch with and now Villa’s Premier League top scorer. I think he’s irreplaceable.”
Meanwhile, Smith is delighted seeing so many of his former players at Villa reaching the top of the game.
He continued: “It gives me great pride. Seeing all those guys I worked with improve, get opportunities, earn more money and ultimately play better.
“I remember telling Ezri (Konsa) when I left that he’s got 18 months to get in the England squad or else I’m allowed a free punch and he texted me back when he got in the squad.
“But it’s great to see what Unai (Emery) has done. And it’s what I expected with the ownership because Nassef (Sawiris) and Wes (Edens) were really intent on their five year plan of getting to Europe.”