Manchester City crashed out of the Carabao Cup after substitutes Erling Haaland and Kevin de Bruyne failed to inspire a fightback in a shock quarter-final defeat to Premier League strugglers Southampton.First-half goals from Saints pair Sekou Mara and Moussa Djenepo stunned the eight-time winners on an extraordinary evening at St Mary's.Pep Guardiola began with Haaland and De Bruyne on the bench for the second successive game ahead of Saturday’s Manchester derby at Old Trafford.But, unlike on Sunday when the influential pair were not required in a thumping 4-0 FA Cup victory over Chelsea, the decision backfired as they were unable to prevent City suffering elimination after coming off the bench in the second period.Battling underdogs Southampton fully merited victory and will face Newcastle in their first League Cup semi-final since going on to finish runners-up in 2017.A remarkable result was Saints’ first home success over Premier League opposition since they beat Chelsea in August and only a sixth since the start of 2022.Southampton overcame League One clubs Cambridge, Sheffield Wednesday and Lincoln to reach this stage but the vast number of empty seats suggested many home fans did not envisage further progression.Yet Nathan Jones’ bottom-of-the-table side set aside their dire league campaign and dismal home form as an aggressive start prevented City slipping into their formidable rhythm and paved the way for a monumental upset.Lyanco epitomised Saints’ steel with his robust early treatment of Jack Grealish and he was instrumental in the 23rd-minute opener.After cutting out Sergio Gomez’s pass to Grealish, the Brazilian defender raced forward and delivered a low cross which Mara emphatically swept past Stefan Ortega