Sangaré's camp is reported to have preferred a move to a club further down the Premier League table, where he would be guaranteed regular starts rather than needing to fight for a place in a bigger squad. Brentford ultimately won the race for his signature after United missed out, paying a club-record fee reported at around £39m to prise him away from Ligue 1 side Lens.
The 24-year-old had enjoyed an outstanding debut season in France following his move from Rapid Wien in the summer of 2025, helping Lens finish second in Ligue 1 and win the Coupe de France for the first time in the club's history.
He made 33 appearances in all competitions, scoring three goals and registering four assists, form that earned him a place in the UNFP Ligue 1 Team of the Year and the Prix Marc-Vivien Foé, awarded annually to the division's best African player.
Brentford head coach Keith Andrews said the club had tracked Sangaré for some time before completing the signing.
"Mamadou is someone that we've tracked for quite some time. He's been on our radar and was a player we were really keen to bring in," Andrews said.
"At Lens, he performed at such a consistently high level for a team that finished second in the league."
Sangaré, who has represented Mali on 16 occasions, has taken an unconventional route to the Premier League, having previously spent loan spells in Austria with Grazer AK and Hartberg before a permanent move to Rapid Wien in 2024. His five-year contract at Brentford includes a club option for a further year, tying him to the club until at least 2031.
The fee comfortably surpasses the £42.5m Brentford paid Bournemouth for Dango Ouattara a year earlier, making Sangaré the most expensive signing in the west London club's history. Crystal Palace had also been credited with interest in the midfielder before Brentford moved to secure his signature, while Rapid Wien stand to benefit from the transfer through a sell-on clause included in his original move from the Austrian club to Lens.
For Manchester United, missing out on Sangaré continues a pattern of high-profile midfield targets slipping through their fingers in recent transfer windows, though the specifics of this deal suggest the player's own preference for regular football, rather than any reluctance on United's part, was the deciding factor.