Barkley has come under scrutiny after a run of inconsistent displays since returning from a hamstring injury last month.
The Chelsea loanee was substituted for the eighth straight match as Villa lost 2-1 to Leicester on Sunday having struggled to make an impression.
But Smith believes the 27-year-old is being unfairly singled out for criticism at a time when several other players are also suffering from fluctuating form.
He said: “It’s a long way off the mark to say things aren’t working out for Ross. His numbers have been really good in terms of his output on the pitch.
“We have to remember he’s been out for six or seven weeks with a hamstring injury and then had to play games to recapture that fitness because we haven’t been able to train.
“But he’s certainly getting back to where we want him to be. I just needed to change the game at that time.”
Barkley’s capture last September on a season-long loan was regarded as a huge coup for Villa and he enjoyed an excellent start to life in the West Midlands, netting on debut as Smith’s team demolished Premier League champions Liverpool 7-2.
The former Everton star also netted a late winner in a 1-0 win at Leicester and impressed in Villa’s emphatic 3-0 win at Arsenal.
But after spending nearly two months on the sidelines through injury, his recent performances have struggled to hit the same heights. Barkley netted his third goal of the season as Villa won 1-0 at Southampton last month yet has otherwise seen his influence limited.
He was seen kicking a water bottle carrier after being substituted in a recent win over Arsenal and while his early showings for Villa sparked talk of a possible England recall, his chances of breaking into Gareth Southgate’s Euro 2020 squad are becoming increasingly remote.
Smith, meanwhile, will weigh up whether to make changes to Villa’s starting XI for Saturday’s trip to Leeds, after Jacob Ramsey and Morgan Sanson both caught the eye coming off the bench against the Foxes.
“That’s what you want as a manager, you want selection headaches,” said Smith.