Real Madrid have agreed personal terms with the 19-year-old Ivory Coast winger and are finalising a deal with RB Leipzig reportedly worth up to €135 million, after Paris Saint-Germain and Liverpool withdrew from the race, according to ESPN.
It caps an 18-month rise from academy trials that went nowhere to a breakout season at Leganés and a move to the Bundesliga. Txema Indias, Leganés's sporting director during Diomande's time at the club, spoke to AS about the player who arrived at Butarque with almost nothing.
"Now, all of us who lived through Diomande's rise here probably want to take some credit, but the medal has to go to the boy, for everything he went through. He's had some very tragic experiences at 19. He tried to get into a lot of countries, had trials at a lot of clubs, even in England, and nothing stuck...
"He ended up at Leganés in the end. He signed in October or November, but we couldn't have him here until March because he had to go back to his country over visa issues. He first appeared with the reserves, played two or three matches and we quickly saw what he had... As soon as we brought him up to the first team we realised his potential.
"We knew he'd have value, but for it to reach this level... nobody could have imagined that. We were lucky to have had En-Nesyri, Braithwaite and Diego Rico, but what's happened with Yan has been a surprise even though you could see he had brutal ability. Leipzig took a big risk paying a significant amount for a player with only 10 top-flight appearances, and it paid off for them," Indias said.
On managing such a young, unsettled arrival, he added: "That's where the coaches are the clever ones, getting the best out of him. At Leganés, when Diomande came through on the right wing, we also had Juan Cruz and Dani Raba, and sometimes all three would be on the pitch at once.
"I think Yan feels more comfortable out on the left, like at the World Cup. He uses his left foot really well, but from the left side, close to the box, he doesn't just offer dribbling, he adds goals, which is what matters most in football."
Asked to rank Diomande alongside Bundesliga rival Michael Olise, Indias said: "Venturing a guess isn't easy, but I think he even has more potential than he's shown. He has goals in him, he can have seasons with a lot of goals from either flank. At his age we don't know where his ceiling is, but he's already taken steps that others take much longer to take.
"In the end people remember the footballer they see on television, but I remember the person. If you look after the person, the performance is better. Yan had moments where he could have fallen apart, like that day against Sevilla when he missed a clear chance in the 92nd minute that could have kept us up, but he never gave up. Olise is a global phenomenon, but I think Yan is at his level in media terms, and he's even younger."
Diomande scored 12 goals and eight assists as Leipzig finished third in the Bundesliga last season and was voted the division's best young player.