Diomandé, 19, impressed at this summer's World Cup for Ivory Coast and is regarded as one of the most promising young attackers in his position anywhere in the world, with Real Madrid closing in on a deal to sign him from RB Leipzig this summer.
The Ivory Coast international spent time under González at Leganés before his move to Leipzig, and the coach recalls being struck by his ability from the very start.
"We couldn't believe how good he was. From the first touch of the ball, you could see he was different," González told Diario AS.
Comparisons are part of elite football, especially between clubs with a fierce rivalry, and Diomandé plays in the same position as Barcelona's Lamine Yamal.
González rates the pair as close to each other in quality: "It might sound crazy, but looking at his trajectory I'd put him at that level. Lamine has had more continuity and has been proving it for longer, but if Yan gets that same opportunity, I think he can reach his level, or even surpass it."
González followed Diomandé's development closely and is clear that the Real Madrid shirt will not be too big for him in terms of talent, though he flagged one caveat.
"He's a supremely gifted talent, and his potential is huge. A phenomenon. That's his level and he's going to show it. He's taken giant leaps and now another one awaits him. My only real question is how he'll respond mentally to the pressure."
Real Madrid have lacked a clear reference point on both flanks for several seasons, though Vinícius Júnior looks the undisputed starter on the left. On that front, the former Leganés captain stressed that Diomandé could perform in different positions: "In Germany I've seen him play a few games on the right, and at the World Cup too, and he's good in both roles. He's very complete and destined to take over the world."
Diomandé began his career far from Europe's traditional academies, moving to the United States as a teenager before joining Leganés in January 2025 and earning a switch to Leipzig within six months, where he established himself as one of the Bundesliga's standout performers.