Southampton scored twice in injury time to book their place in the third round of the Carabao Cup courtesy of a thrilling 5-3 victory over Championship side Cardiff City in south Wales.
Debutant Mateus Fernandes put the Premier League outfit ahead before Rubin Colwill - fresh from being omitted from the Wales squad - levelled with a thumping hit in front of national team boss Craig Bellamy.
Sam Amo-Ameyaw restored Southampton's lead with his first senior goal, although Ronnie Edwards' own goal early on in the second half made it 2-2.
Cameron Archer then notched his first goal since joining Southampton from Aston Villa to put the Saints ahead again, with substitute Alex Robertson equalising with a fine volley just two minutes later.
But James Bree and Archer both struck in additional time as Russell Martin's side edged a thriller in the Welsh capital.
The Saints dominated possession early on and needed just 10 minutes to go in front as Tyler Dibling embarked on a mazy run before finding Fernandes who drilled beyond Jak Alnwick from the edge of the 18-yard box.
Amo-Ameyaw then rounded goalkeeper Alnwick but was unable to shoot from an acute angle after taking a heavy touch.
And Cardiff levelled in spectacular fashion against the run of play on 21 minutes as Colwill - who scored in the Bluebirds' opening round win over Bristol Rovers - rifled home via the underside of Joe Lumley's crossbar from 30 yards out.
The Bluebirds were pegged back nine minutes after levelling as, following a slick passing move, Charlie Taylor picked out Amo-Ameyaw who bent an effort past Alnwick from the edge of the Cardiff box.
A frenetic encounter continued to produce real entertainment and Cardiff fought back four minutes into the second-half as goalkeeper Lumley palmed Raheem Conte's cross into the legs of Edwards who was helpless to watch the ball trickle into his own net.
Southampton remained patient and made it 3-2 in the 55th minute as Archer spun beyond Dimitrios Goutas before drilling home, only for former Man City midfielder Robertson to volley home two minutes later as Cardiff equalised for a third time.
The tie appeared destined to go to a penalty shootout until James Bree's fierce strike dipped over Alnwick in the first minute of injury-time, with Archer coolly slotting home his second three minutes later to earn Southampton their first win of the campaign.
Cardiff City boss Erol Bulut:
"We can take a lot of positives from the game when we see the youngsters playing against a Premier League club.
"We had it in our hands at one stage and had Cian Ashford hit the target with his big chance it might have been different.
"But they showed their quality and experience in the end. It was disappointing to concede just a few minutes into added time. It would have been nice and exciting to have taken it to penalties."
Southampton boss Russell Martin:
“I’m really happy with the win and I’m pleased for my young players. But there is also a lot to be annoyed about.
“We conceded three goals and the game descended into chaos in the second half. It was a moment of brilliance for their first goal from a player I have admired for a long time (Rubin Colwill), but we took our foot of the gas and dropped their intensity.
“That was a big learning curve for the younger players. They took some liberties in the first half and they will be better for the experience and they showed real grit.”