Southamtpon’s unbeaten start to the Championship season came crashing to an end as Russell Martin’s side were blown away 5-0 by brilliant Sunderland at the Stadium of Light.

Sunderland fans taunted Ross Stewart after the injured striker’s deadline-day switch to Saints as Tony Mowbray’s side built on a dream start and stunned the visitors.

Jack Clarke scored the opening goal after just 52 seconds before Pierre Ekwah added a deflected second six minutes later.

The outstanding Ekwah scored his second and Sunderland’s third on the stroke of half-time. Bradley Dack added a fourth early in the second half before 16-year-old substitute Chris Rigg rounded off a perfect afternoon with his first league goal in the fifth minute of stoppage time.

The win means Sunderland – who signed four players on deadline day, including Chelsea loanee Mason Burstow – are now unbeaten in three games.

In the week boss Mowbray marked his first anniversary as boss, the Black Cats delivered their best performance of his tenure so far.

A fine opening goal inside a minute set Sunderland on their way. Abdoullah Ba found Trai Hume on the right and the full-back delivered a teasing cross that was met by winger Clarke, who ghosted in at the back post to head home.

Ba was again involved in the second six minutes later. After a Jobe Bellingham cut-back, the winger, only in the team because of the injury to Patrick Roberts, who Southampton tried to sign this week, teed up Ekwah on the edge of the box and the former West Ham midfielder found the bottom corner from 25 yards.

After their nightmare start, Southampton settled down and tried to get a grip of the game. In a dominant 10 minute spell, Martin’s side had 91 per cent of possession but failed to find the goal they needed after the horror opening.

And rather than sit back and soak up pressure, Sunderland then pushed for more goals.

The third came in the 45th minute when Ekwah pounced on a mistake by Southampton debutant Mason Holgate and curled into the bottom corner from 25 yards out.

Southampton made two substitutions at the break, introducing Che Adams after his deadline-day move to Wolves fell through and Newcastle loanee Ryan Fraser. But the changes did not have the impact Martin had hoped for and within four minutes of the restart Sunderland had their fourth.

Gavin Bazuna saved well to keep out a header from Dack but the home side kept the ball alive and the former Blackburn man poked home from close range.

Sunderland put the icing on the cake in the 95th minute when Rigg headed in a cross from fellow substitute Jewison Bennette.