The move came after Manchester-born Rashford, who made 426 senior appearances and scored 138 goals for United in all competitions, fell out of favour with manager Ruben Amorim.
The win leaves United in 15th place in the Europa League standings on six points from four games.
The 33-year-old Son, who is under contract until 2026, is set to leave Spurs after a decade.
IMAGES from football matches played across Europe on Friday.
Son Heung-min said he is "here to win" after he joined Los Angeles FC for a record Major League Soccer transfer fee, ending a decade-long stint at Tottenham Hotspur.
Winning back-to-back titles for the first time since 1984 is likely to prove a rather more arduous challenge for Liverpool.
Man United boss Amorim says he has no plans to quit
IMAGES from the Europa League matches played on Thursday
In an early match, Norwegian side Bodo/Glimt secured a 3-2 home victory against FC Porto thanks to a brace from Jens Petter Hauge, despite going down to 10 men in the 51st minute.
Thomas Frank will take charge of a club that will take part in next year's Champions League after they won the Europa League last month in Bilbao.
IMAGES from the Europa League matches played on Thursday
Xabi Alonso has signed a three-year contract until June 2028 and the 43-year-old replaces Carlo Ancelotti, who took charge of his last game on Saturday.
>Manchester United's star centre-back Harry Maguire was spotted in Mumbai on Thursday, May 29, 2025, exploring the local food scene and connecting with the community.
Lazio, who had won all four previous games, were held to a frustrating scoreless draw by a Bulgarian side who came to defend.
The 23-year-old Palmer's two assists in five minutes during the second half turned the match around for Premier League club Chelsea and his efforts saw him named Player of the Match.
The other semi-final will see an Italian side, Milan or Roma, come up against Bayer Leverkusen or West Ham.
Images from Friday's Premier League matches between Chelsea and Manchester United, Aston Villa and Tottenham Hotspur.
Rasmus Hojlund scored an equaliser deep into stoppage time as Manchester United salvaged a 1-1 away draw at 10-man Bournemouth in the Premier League on Sunday.
When art steps off the canvas and onto the red carpet, the result is pure visual poetry.
Atalanta beat Bayer Leverkusen 3-0 in the Europa League final
Summary of the Europa League semi-final matches played on Thursday.
Qarabag had chances, Tural Baymarov missing from the penalty spot just before the hour mark and Junior hitting the woodwork, but Spurs stayed in control of the match.
'We've been talking during this week and now it's the right moment to announce it.'
Sevilla dismissed their manager Javier Garcia Pimienta on Sunday, two days after their 0-1 defeat at Valencia, marking their fourth consecutive LaLiga loss.
Nuno Espirito Santo's side took the lead after five minutes when a corner fell to Elliot Anderson on the edge of the area and his powerful deflected drive found the net.
A round-up of Saturday's action the Bundesliga, Ligue 1
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.
Manchester City and Chelsea both secured their Champions League places with victories on the final day of the English Premier League season and Newcastle United joined them despite stumbling to a last-day defeat.
Rennes denied late Europa League equaliser due to little-known rule
IMAGES from the Europa League semifinal matches played on Thursday.
A round-up of Thursday's Europa League Round of 16 second leg matches.
Francisco Moura's second-half strike earned hosts Porto a 1-1 draw against 10-man AS Roma in the first leg of their Europa League knockout round play-off on Thursday.
Real Madrid fight back to beat Mallorca and put Barca party on hold
Liverpool will take on LASK, Union Saint-Gilloise and Toulouse in the Europa League group stage while debutants Brighton & Hove Albion will face Ajax Amsterdam and Olympique de Marseille following the draw on Friday.
Newcastle United registered a 2-0 home win over Chelsea on Sunday that moves the Magpies a step closer to Champions League football next season.
Jose Mourinho's side top Group G with a maximum nine points, three clear of second-placed Slavia.
Son Heung-min said returning to his home country South Korea for the World Cup qualifiers against Oman and Jordan has brought him immense joy
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.
Liverpool roared back from a goal behind to thrash Tottenham Hotspur 5-1 and wrap up the English Premier League title in style.
Chelsea beat London rivals Tottenham Hotspur 1-0 on Thursday thanks to a goal by Argentina's Enzo Fernandez