FOR all the understandable focus on efforts to strengthen the squad, specifically the forward line, in the final stages of the window, Sunderland's most important business wasn't necessarily who they signed, rather who they managed to keep.

Yes, Ross Stewart left for Southampton on deadline day and Mowbray was sad to lose "amazing men" Danny Batth and Lynden Gooch, but when the phone rang for the likes of Patrick Roberts, Jack Clarke and Pierre Ekwah, the answer from the Black Cats was emphatic.

"I need to go on the record and say great credit to the owners," said Mowbray after Saturday's quite sensational 5-0 annihilation of Saints.

"There are some big numbers for some of these footballers and we're trying to build the club, we're not trying to get rid of the club."

With Mowbray in the dugout, Ekwah bossing the middle of the park and Clarke on the flank, the future is bright for Sunderland, even without Stewart, who must have had mixed emotions watching the side for whom Russell Martin would say afterwards the striker "loved" playing for tear his new employers to bits.

Whatever Stuttgart bid for Ekwah, it wasn't remotely close to what the imposing central midfielder is worth now and could be worth a year or two down the line. He was playing a different game to everyone else on the pitch on Saturday. It all looked so incredibly easy. He's quite the talent.

As is Clarke. Burnley discovered this summer how highly Sunderland rate the flanker, who set the Black Cats on their way to the best win of Mowbray's tenure so far with the opener after just 52 seconds.

Mason Burstow was introduced to the supporters before the game on the Stadium of Light pitch. The Chelsea forward was reportedly wanted by AC Milan but instead opted for the Wearside switch. Sunderland played like a team in the Champions League rather than the Championship against the stunned Saints. Five goals without a striker.

It was the most remarkable end to a hugely dramatic 72 hours, even by Sunderland's standards. The last two days of the window were riddled with twists and uncertainty but the Black Cats came out of it as well as they could have hoped.

Four new signings and, in plain terms, a very good deal for a striker - regardless of his quality - who has been injured since January and was set to leave on a free next summer, with no sign of a contract breakthrough in sight.

The Stewart deal "suits everyone" said Southampton boss Martin, who tried and failed to sign Roberts as well.

Mowbray bumped into the injured Roberts after the game on Saturday and joked that he wouldn't get back into the team after the international break. Such is his talent and importance, he will, but Abdoullah Ba had his best game in a Sunderland shirt on the right flank, having a hand in three of the five goals.

He set Trai Hume away on the right, with the full-back crossing for Clarke for the first before teeing up Ekwah on the edge of the box for the second.

Given the conversations visiting boss Martin had with his players before kick-off, you could understand his frustration.

"The one thing we spoke about is starting well," he said.

"It's a young team at Sunderland and when the wind is in their sails they're very good but when they have a difficult start they can then find it tough to get the game back.

"But the game just went for them. They had momentum after their start, brilliant momentum and we didn't have enough of that."

Ekwah effectively wrapped up the game with his second goal late in the first half, before Bradley Dack got in on the act just after the restart. Just when you think it couldn't really get much better, Jewison Bennette comes off the bench and turns into Maradona and Chris Rigg, 16, heads in a fifth.

"It's a good day today," said Mowbray, an early contender for understatement of the season.

"You know and I know we'll sit here over the course of the season and we'll have lost a game and the questions will be a bit more difficult. But as a coach you have to trust your players and let them express their talent."

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For all his brilliance when fit, Sunderland have shown since January that they can cope without Stewart.

"Sometimes you have to make some really tough decisions," said Mowbray.

"Danny Batth and Lynden Gooch are really tough decisions but if the quality comes in, I've always said, the king is dead, long live the king.

"Mo Salah at the minute is who the world seems to be talking about. Once he goes for his £200m, someone else will fill the void and bang in 20-odd goals for Liverpool. They will, because they're a great team who create chances so someone will eat them up and bang them in the back of the net. You move on, as they've had to do with Suarez and Ian Rush and Michael Owen and Robbie Fowler.

"I've just been stood there with Kevin Phillips. The next one is around the corner, the opportunity to come and grasp it and become the next hero."