Simeone's side could not prevent the Ghana international heading to the Emirates after his £45m release clause was triggered by the Gunners, who tied Partey down to a long-term deal in North London, with Lucas Torreira heading in the other direction on loan.
Simeone was said to be left seething at the situation, but the former Argentina international has now accepted the reality of the situation and is certain that Partey will make a name for himself at Arsenal.
Speaking to reporters ahead of Atletico's La Liga showdown with Celta Vigo on Saturday, Simeone said: "In these situations of the clauses we cannot give many opinions. They are decisions that are made based on that possibility that exists.
"As for Thomas, everything that happens to the guys who have given me a lot makes me happy. I remember the games we saw him with the B team and when he started to come through.
"He went to Almeria, it was difficult for him to find a stable place but he is an extraordinary player. He will do well and we wish him the best. We love him very much."
Partey is in contention to make his Arsenal debut on Saturday evening when Mikel Arteta's side travel to the Etihad to take on Manchester City in the Premier League.