On a day when their rivals contested the Premier League title, Manchester United produced another performance that showed why they could not even reach the Europa League. Leaden-footed for long periods, they fell behind at St Mary's to a goal from Rickie Lambert, before equalising in the second half with a rare flash of class from Juan Mata. The match then petered out as both teams seemed to turn their thoughts to the future: rebuilding begins immediately for both clubs.

Ryan Giggs admitted that his brief reign as Manchester United manager is set to end this week, most likely with the appointment of Louis van Gaal, while Mauricio Pochettino suggested that he will take a lot of persuading to remain at Southampton. Furthermore, both teams fielded players who might have been making their final appearances for their clubs, with several Southampton youngsters likely to be the subject of summer bids from title-chasing clubs and several United players likely to take a step down.

Three of the back four that began for United here probably will not be at the club next season and it would be no surprise if one of them, Patrice Evra, was replaced by the youngster who was his counterpart in this game, United being among several clubs coveting Luke Shaw.

In front of the watching England manager, Roy Hodgson, Shaw and Adam Lallana were the best players on the pitch, both heavily involved in everything inventive that Southampton did, especially in a first half dominated by the hosts. Shaw made regular incursions from the left and headed narrowly over the bar early on after an exchange of passes with Lallana.

United were being overrun in midfield and Nemanja Vidic and Rio Ferdinand were stodgy in central defence. After the Serb was dispossessed by Victor Wanyama in the 24th minute, a curling shot from Lallana forced a save from David de Gea. Two minutes later Vidic was beaten in the air by Lambert, who inadvertently bloodied the defender's nose with his elbow. To the fury of United, the referee, Mike Dean, allowed play to continue and Steve Davis slipped in Lambert to finish smartly from 12 yards. A controversial goal but there was no doubt the better team had the lead.

Giggs replaced Shinji Kagawa with Michael Carrick at half-time in a bid to gain a foothold in midfield. The plan worked, as United improved slightly. They were rewarded with an equaliser in the 54th minute when Mata flighted a delicate free-kick over the wall and into the top corner. That was pretty much it as far as the action was concerned.

Pochettino then withdrew Lallana and Shaw: he said both were tired but it felt like he was giving the crowd a chance to bid farewell to the players. They may have seen the last of the manager, too: he has a year left on his contract but other clubs admire what he has done at Southampton, who will meet the Argentinian on Monday to establish whether they can make the sort of investment to convince him to stay.

"We're going to sit down and talk," said Pochettino. "This is the end of a five-season project that started with Markus Liebherr buying the club and appointing Nicolas Cortese as chairman. This project has now come to an end and we achieved what we wanted, to take the club from League 1 and establish it in the Premier League. Now a new project has to start.The board has to decide how that happens. Whether it's a two-year, three-year, four-year or five-year project, we'll see."

Giggs knows he will not remain United manager but gave no indication about his next move. "The managerial situation will probably be sorted out in the next week and then I'll need to think about my own position – whether to play on or not, to stay on in the staff and what position that's going to be, whether I take a year out of football, these are the decisions I have to make. I'll look at everything."

Man of match Luke Shaw(Southampton)