Five minutes later, a brutal roundabout shot from Stuart Armstrong, who ricocheted on the back of James Maddison and evil goalkeeper Kasper Schmeichel, and Danny Ings' 16th goal of the season at nine minutes gave Southampton a win largely deserved against a exhausted. city side.
However the Saints fought back to make it four wins from their last five league matches.
For City, it's now a direct defeat at King Power Stadium and just one point out of a possible nine at home when Brendan Rodger's team has recently stalled in front of their own fans.
VAR played a major role, ruling out three Leicester offside goals and a penalty for Saints, but Hasenhuttl was far from concerned about the interruptions.
Eight minutes later Leicester capitalised. Ayoze Perez quickly thought when he was fouled by Ryan Bertrand and saw that he quickly sprayed a free kick into the left room that Jamie Vardy could run into. It was the first time that the Belgian was able to shoot past Alex McCarthy from six meters.
Leicester took the lead through Dennis Praet in the 14th but conceded an equalizer five minutes later when Stuart Armstrong's shot deflected in.
After Schmeichel had palmed away a first-time half-volley from Pierre-Emile Hojbjerg that bounced awkwardly in front of him, and Vardy rightly had a goal ruled out by VAR for offside, Ings then twice hit the woodwork in the 43rd minute, with his second effort a stunning first-time half-volley from 16 yards. His second attempt was a breathtaking first half volleyball Batch from 16 meters.
However he also refused to be too harsh on them.
Long, though, appeared to be offside in receiving a through-ball, with Soyuncu protesting his innocence.
The screens inside the ground suggested VAR was checking the penalty decision, but via the television screens in the press box it could be seen those in Stockley Park were looking at the offside first.
Kelechi Iheanacho has now turned his attention to Saturday's Premier League encounter with Southampton.
After 90 seconds it was determined Long's shoulder was marginally ahead of that of Soyuncu, leading to the penalty decision being overturned and Mason nodding to Soyuncu the booking would also be rescinded.
Nine minutes before the end, Ings scored the goal he deserved and slid the ball between the flattering legs after being substituted by Che Adams, who had been substituted just three minutes earlier.