Newcastle United boss Eddie Howe has warned that the job is only half done, as the club moved a step closer to a first domestic final in almost a quarter of a century.
A second half goal from Joelinton was enough to seal the 1-0 win for the Magpies at St Mary's Stadium, giving them a one-goal cushion ahead of the return leg at St James' Park on Tuesday.
It was a cagey affair, with both sides seeing a goal ruled out for hand ball. Joelinton's 39th minute strike was adjudged to have hit his arm in the buildup while former Newcastle academy prospect Adam Armstrong's equaliser was also chalked off after a VAR review.
Newcastle United keeper Nick Pope was called into action twice in the second half to deny Southampton's Che Adams, extending his run of clean sheets to ten consecutive games.
Southampton ended the game with ten men after Duje Ćaleta-Car was shown a second yellow card after bundling over Allan Saint-Maximin in the closing stages.
Head coach Eddie Howe said: "It was very tight. I don't think we were at our best today but I think we did enough to deserve to win. There was a lot of talking points, obviously VAR involved, but delighted to win.
"It's half time, we're 1-0 up. That's all it is. I'm pleased with our work tonight but there's a long way to go.
"Unfortunately in my playing career, I felt so many disappointments from potential moments of success - but from my side, I'm very calm and very level and I know there's a lot of work to do."
Newcastle have only reached the final of the League Cup once in their history, losing the 1976 final 2-1 at the hands of Manchester City.
If they were to progress to Wembley and lift the trophy, it would be the first silverware the club had won since lifting the Inter-City Fairs Cup in 1969.
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