The Welshman proved to be decisive as he acrobatically denied Manolo Gabbiadini's free-kick that looked destined for the top corner in the closing stages of regulation time, before also stopping the Italian's effort in the penalty shootout.
'He made fantastic saves'
That save, coupled with Nampalys Mendy's winning penalty, took the Foxes through to the fifth round of the competition, where they face a daunting home clash with Pep Guardiola's Manchester City.
Puel stated that the team were indebted to Ward following the game. Talking to LCFC.com, the Frenchman said: "We have a fantastic goalkeeper for penalties. He made saves, it was the same thing at Wolves. He made the same thing today (Tuesday) with his last penalty.
“He made fantastic saves in the game also."
He was also key in the previous round as again the Foxes edged past Wolverhampton Wanderers on penalties.
'It's just details that make the difference'
With the game being decided by a penalty shoot-out, Puel also highlighted how close-fought the match was between the Foxes and his former side, and suggested that Leicester were slightly fortunate to progress.
He said: "It’s a fantastic feeling of course, all was not perfect because we have some players without the rhythm and game time and they cannot maintain all the same level for the whole game.
“We played this game with good spirit, not all the time the right quality but it was a close game and I think these two teams are close and it’s just details that make the difference."
Leicester are back in action on Saturday afternoon, this time in the league, as they host Watford at the King Power Stadium.