Manchester United crashed out of the Carabao Cup on Wednesday night when they were beaten by Championship side.
Smith’s turn and strike in the final minute of time added on booked a semi-final against Premier League leaders Manchester City.
The hosts went ahead after an hour mark when Joe Bryan’s rasping left-foot strike across goal into the top corner but the lead lasted for just eight minutes as Zlatan Ibrahimovic marked his first start since April with a goal by firing home a low free kick
There were jubilant scenes at the final whistle, with much of the sell-out crowd rushing on to the pitch in celebration and taking selfies with some of the City players.
Despite fielding a side showing 10 changes, United manager Jose Mourinho had recalled Paul Pogba after a three-match ban and picked a forward line of Ibrahimovic, Marcus Rashford and Anthony Martial. He later introduced Striker Romelu Lukaku who was unable to make any impact in the match.
In another encounter, Spanish striker, Alvaro Morata rescued Chelsea with an injury-time goal to secure a semi-final with their London Rivals, Arsenal.
Willian opened the scoring, capping a fine team move which resulted in Cesc Fabregas squaring for the Brazilian to tap home.
Bournemouth thought they had forced extra-time when Dan Gosling curled home from the edge of the box in the final minute after being picked out by Callum Wilson.
But substitute Morata sent Conte’s team into the last four when he finished from Eden Hazard’s backheel.