The 33-year-old Son, who is under contract until 2026, is set to leave Spurs after a decade.
United manager Ruben Amorim's tough start to life at Old Trafford continues though and the Portuguese has now lost eight of the 14 Premier League matches since he took charge.
Ange Postecoglou ultimately paid the price for an horrendous English Premier League season which saw Tottenham finish 17th.
Images from the Europa League semi-finals first Leg between Athletic Bilbao and Manchester United, Tottenham Hotspur and Bodo/Glimt.
Chelsea beat London rivals Tottenham Hotspur 1-0 on Thursday thanks to a goal by Argentina's Enzo Fernandez
Liverpool roared back from a goal behind to thrash Tottenham Hotspur 5-1 and wrap up the English Premier League title in style.
Arsenal defeated London rivals Chelsea 1-0 for their first win in four Premier League games on Sunday as a headed goal by stand-in striker Mikel Merino boosted their faint hopes of catching up with runaway leaders Liverpool.
A round-up of Thursday's Europa League Round of 16 second leg matches.
United climbed to fourth in the standings on 15 points going into the last round of matches, in a strong position to reach the knockout phase along with Spurs who are sixth with 14 points.
A summary of Saturday's action in the English Premier League.
A stoppage-time finish from Rayan Cherki earned Olympique Lyonnais a dramatic 2-2 draw with Manchester United in the first leg of their Europa League quarter-final.
IMAGES from the Premier League matches played on Sunday.
A summary of Thursday's Europa League quarter-finals second-leg.
Joshua Zirkzee scored the winning penalty for 10-man Manchester United against Arsenal after their hectic FA Cup third round tie finished 1-1 after extra time.
Postecoglou moves a step closer to making good on his reputation for securing silverware in his second season at clubs and delivering a first cup for Spurs since they won the League Cup in 2008.
Tottenham Hotspur's Brennan Johnson, Dejan Kulusevski and Dominic Solanke got on the scoresheet in a 3-0 victory over 10-man Manchester United in the Premier League on Sunday as the visitors ran roughshod over the bedraggled Old Trafford side.
IMAGES from the English Premier League matches played on Sunday.
United are 13th in the Premier League table and following a 1-1 draw with Dutch side Twente Enschede in the first Europa League match, Ten Hag said speculation about his job was inevitable.
Moises Caicedo's blistering second-half strike cancelled out a Bruno Fernandes penalty as Chelsea salvaged a 1-1 draw with Manchester United on Sunday.
Manchester City have now won only once in 11 games in all competitions.
Manchester City thrashed West Ham United 4-1 in the Premier League on Saturday to claim their first back-to-back wins since October.
Brazilian Richarlison missed a golden opening to win it at the death and Spurs had to settle for one point in a match they really should have taken all three from.
Images from the English Premier League matches played on Sunday night.
IMAGES from the English Premier League matches played on Sunday
IMAGES from the Premier League matches played across England, on Sunday.
A brilliantly-worked goal by Ryan Christie and a Justin Kluivert penalty gave Bournemouth shock 2-0 Premier League win at home to 10-man Arsenal.
England begin their World Cup group campaign against Iran on November 21.
While England boast a formidable attacking threat, there are concerns about their defence which is perhaps why Southgate is prepared to look at new candidates before he has to make his final call for the tournament.
Tottenham Hotspur hammered 10-man Aston Villa 4-0 in the Premier League on Sunday thanks to four second-half goals, allowing them to close the gap with their Birmingham rivals to two points in the chase for Champions League football next season.
IMAGES from the Premier League matches played on Saturday.
Manchester City clinched a 1-0 victory at Tottenham Hotspur, while Chelsea were held to a 0-0 draw at home by Aston Villa.
Mohamed Salah scored a late equaliser from a penalty kick as Liverpool escaped Old Trafford with a single point in a 2-2 draw with Manchester United to climb to even on points with Premier League leaders Arsenal.
Tottenham Hotspur opened a five-point lead at the top of the Premier League with a 2-1 victory at Crystal Palace as their unbeaten start to the season continued on Friday.
The victory moved United up to fifth with nine points from five matches, six adrift of leaders Arsenal and four behind second-placed Manchester City. Leicester stay bottom on one point.
All the latest news from the summer transfer window...
Liverpool snatched three points with a wild 1-0 victory over relegation-threatened Nottingham Forest.
IMAGES from the English Premier League matches played on Sunday
IMAGES from the Premier League matches played on Saturday.
A summary of Saturday's action in the Euro 2024 qualifying matches.
Images from Premier League matches played on Sunday.