Goals from January signings Bruno Guimaraes and Chris Wood gave the visitors a 2-1 win tonight.
The game, which had originally been due to be played on January 2, was postponed due to Covid-19 cases and injuries on Tyneside amid unhappiness from Southampton manager Ralph Hassenhuttl that Newcastle would strengthen before the new date.
Hassenhuttl, of course, was right. Howe’s new signings were instrumental in this success, and the fixture was decided by a stunning piece of skill from Guimaraes on what was his full debut.
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The £35million midfielder, signed from Olympique Lyonnais on deadline day, had replaced the injured Joelinton in the starting XI.
Allan Saint-Maximin, meanwhile, was not involved because of illness.
Newcastle, backed by 3,300 noisy fans, had the better of the first 20 minutes. Guimaraes tried his luck from outside the box early in the game, but his shot was headed away for a corner by Jan Bednarek.
Fabian Schar then gave Howe a scare when he went down holding his groin. Howe quickly sent out Jamaal Lascelles to warm up, but Schar, an ever-present since early November, was able to play on after treatment.
Southampton settled into the game, and Armando Broja forced forced a save from Martin Dubravka after a quick break forward. Dubravka, however, could do nothing to stop a deflected header from Stuart Armstrong in the 25th minute.
Kyle Walker-Peters had delivered a ball from the left, and it was headed back across goal by Mohamed Elyounoussi to Armstrong, whose effort went in off Dan Burn.
Newcastle haven’t conceded too many sloppy goals in recent months, and will have been frustrated at the build-up to the strike.
Southampton’s lead was short-lived. The ball was worked to Jonjo Shelvey in a deep position on the left, and he came inside on to his right foot and delivered a cross for Wood.
Wood read the inswinging ball and got ahead of Mohammed Salisu to emphatically head home past Fraser Forster to open his United account at the eighth time of asking.
The relief was clear on Wood’s face as he celebrated the strike with his team-mates as the club’s travelling fans celebrated at the other end of the pitch behind Martin Dubravka’s goal.
Che Adams struck the crossbar before the break, and Newcastle’s players left the pitch knowing they had been too open at times.
After a half-time break which saw Dirty Cash, Loaded, Price Tag, Can't Buy Me Love and Money, Money, Money played at the St Mary’s Stadium, it was time for three of United’s January signings to combine for a second goal.
A Matt Targett cross was headed back across goal by Burn, and Guimaraes scored with a stunning backheel flick.
Guimaraes, suffering from cramp, made way for Sean Longstaff in the 66th minute.
Miguel Almiron and Javier Manquillo were also sent on, and Dubravka and his team-mates dealt with everything Southampton threw at them in the last 20 minutes to claim three more important points.
NEWCASTLE UNITED: Dubravka, Krafth (Manquillo, 90), Schar, Burn, Targett, Shelvey, Willock, Guimaraes (Longstaff, 66), Murphy, Fraser (Almiron, 85), Wood. Subs not used: Darlow, Dummett, Lascelles, Ritchie, Gayle, De Bolle.