Middlesbrough have won only one of their last 16 League games and this defeat sent them to the bottom of the Premiership table. They looked mere shadows of the side that had knocked Liverpool out of the Coca-Cola Cup in midweek.
A dour game was settled by a disputed second-half penalty. Clayton Blackmore handled on the line to keep out Ken Monkou's header from a corner and was immediately sent off by the referee Gerald Ashby - who also booked seven other players - before Jim Magilton converted the penalty.
Robson fumed over the award of the corner in the build-up to the penalty. "Everybody in the ground saw it wasn't a corner," he said. "I thought that the referee and his assistants had a very poor game.
"His control of the game was very poor. He let a few early fouls on Emerson and Juninho go unpunished and that meant Southampton could keep on doing it for the rest of the first half. It helped them because the number of fouls meant they could break the game up and then regroup and get men behind the ball."
Defeat leaves Middlesbrough with a long battle ahead to avoid relegation, but Robson said: "I would rather be bottom now, when there's a lot of football to be played and when there's something we can do about it."
Robson, who angrily denied reports that he had offered to resign, may need to take a lesson from his Southampton counterpart, Graeme Souness, who in an attempt to improve on his team's dreadful away form relegated his star player, Matthew Le Tissier, to the bench.
Souness undoubtedly sensed what sort of a game it would be - a hard-fought battle in which flashes of skill were few and far between. "We've played better football in every away game but we showed a bit of grit and determination today and defended well," Souness said.
Goal: Magilton (59 pen) 0-1.
Middlesbrough(3-5-2): Walsh; Cox, Whyte, Vickers; Blackmore, Fleming, Emerson (Stamp, 76), Mustoe, Juninho; Ravanelli, Hignett (Beck, 76). Substitutes not used: Liddle, Fjortoft, Roberts (gk).
Southampton (3-5-2): Taylor; Van Gobbel, Neilson, Monkou; Berkovic (Le Tissier, 71), Benali, Magilton, Robinson (Charlton, 89), Oakley; Ostenstad (Slater, 81), Hughes. Substitutes not used: Dryden, Beasant (gk).
Referee: G R Ashby (Worcester).
Bookings: Middlesbrough Cox, Emerson, Hignett; Southampton Van Gobbel, Taylor, Berkovic.
Man of the match: Magilton. Attendance: 29,509.Reuse content