Buttler was included in a 12-man squad along with uncapped spinner Dom Bess for the first Test against Pakistan at Lord’s next week.
This was despite Buttler having last played Test cricket some 18 months ago. But Smith is confident Buttler’s recent good form in the Twenty20 Indian Premier League can be carried into the Test arena.
Buttler has endured a frustrating 18-match Test career since making his debut four years ago.
In part this has been as a result of being viewed as both a wicket-keeper and a batsman.
But Smith wants Jonny Bairstow to retain the Test gloves.
Buttler is now set to play as a specialist number seven batsman in an England order where captain Joe Root will move up to three and Bairstow five against a Pakistan side who beat Test newcomers Ireland by five wickets at Malahide on Monday.
Number three was a spot occupied by James Vince but he has now been dropped by England despite making an unbeaten double century for Hampshire on Monday.
“The way we wanted to structure the side was to get the key run scorers in those positions — Joe at three, Jonny at five,” said Smith.
Buttler has yet to hit any great heights in Test cricket but former England batsman Smith said: “We feel it’s the right thing, at the right time with the right player. It was a very strong feeling that we wanted to invest opportunity in Jos.
“His overall Test record, he averages 31, to some extent that’s beside the point — because he’s evolved since then, he’s become an even better player in the short form of the game,” Smith added.
Vince, a shock recall for England’s eventual 4-0 Ashes series loss in Australia, made 83 in the first innings at Brisbane in November and ended his southern hemisphere tour with 76 against New Zealand in Christchurch last month.
But he also repeatedly got out when well-set and the 40-year-old Smith, who played three Tests for England in 2003, remains among those yet to be convinced by Vince.
“James Vince playing well is a terrific player to watch,” he said Smith, “However, and this is what I said to him…he has not produced the runs he should have done.”