Former United winger Anthony Elanga came back to haunt his former club with a stunning solo effort after just five minutes at the City Ground to earn all three points for Nuno Espirito Santo’s side.
Third-placed Forest extend their lead over Newcastle in sixth to 10 points.
Thanks to the strong performance of English sides in European competitions this season, the top five will almost certainly qualify for the Champions League.
Forest are two-time European champions but have not played in the continent’s elite competition since they were holders in 1980.
Elanga was discarded by United in 2023 after a bright start to his career at Old Trafford, but is one of many Forest success stories fulfilling his potential under Nuno.
The Swedish international collected possession deep inside his own half but showed blistering pace to burst into the United box before firing low past Andre Onana.
Just a year after battling to narrowly avoid relegation, Forest are enjoying an unexpected fairytale season that also includes progressing to the FA Cup semi-finals for the first time in 34 years.
They had been forced through 120 minutes and penalties to beat Brighton in Saturday’s quarter-final and were also without top scorer Chris Wood due to injury.
Forest fatigued in the second half, but United were undone by a familiar lack of cutting edge going forward.
Ruben Amorim resorted to sending on centre-back Harry Maguire as a makeshift striker in the closing stages and he nearly grabbed an equaliser in stoppage time when his shot was cleared off the line by Murillo.
United remain without two consecutive Premier League wins all season with the Red Devils languishing down in 13th.
Arsenal maintained some pressure on leaders Liverpool by cutting the gap at the top to nine points.
Saka stole the headlines by coming off the bench to head in on his first appearance since December 21.
Mikel Merino’s deflected effort had given Arsenal a first-half lead. However, victory came at a cost as key defender Gabriel Magalhães limped off injured.
Rodrigo Muniz pulled a goal back in stoppage time, but defeat is a blow to Fulham’s ambitions of European football next season.
Just one week away from the Gunners’ Champions League quarter-final, first leg against Real Madrid, the sight of Gabriel pulling up with a hamstring problem added to Mikel Arteta’s injury woes.
Arsenal are already without forwards Kai Havertz and Gabriel Jesus due to season-ending injuries.
But Merino has proved an able deputy as a stand-in striker.
The Spanish midfielder took his tally to five goals in eight games in his new role, albeit with the aid of a big deflection to open the scoring on 37 minutes.
Saka’s introduction was greeted with the biggest cheer of the night until that point at the Emirates Stadium when he replaced Ethan Nwaneri 25 minutes from time.
The England international took just eight minutes to net his 10th goal of the season.
Saka was in the right place to head in from close range after Gabriel Martinelli flicked on Merino’s cross.
At the bottom of the table, Wolves pulled ever closer to survival with a 1-0 win over West Ham.
Jorgen Strand Larsen scored the only goal at Molineux as Wolves moved 12 points clear of the relegation zone. (AFP)
