The 31-year-old was reportedly a candidate for the manager's jobs at Arsenal and Real Madrid over the summer, and is a "very good friend" of City boss Guardiola, said Begiristain.
Juventus director Giuseppe Marotta backed up Mendes' criticism, expressing the Italian side's disappointment.
Group G: Real Madrid, Roma, CSKA Moscow, Viktoria Plzen.
Three more former European champions Bayern Munich, Benfica, Ajax are together with underdog AEK Athens in Group E.
They were drawn in Group C for this year's group stage of the tournament, alongside PSG, Napoli and Red Star Belgrade.
Instead, it was another Madrid hero, Luka Modric, who was named top performer overall, as chosen by 60 coaches from the Champions and Europa League competitions and 55 journalists from across Europe.
Group A: Atletico Madrid, Borussia Dortmund, Monaco, Club Brugge.
Inter are returning to the competition for the first time in seven seasons.
Thursday night was a big one for European football, with the Champions League draw for the 2018/19 campaign taking place in Monaco.
"They're on a different level - you can maybe be up there with them one year, but not the next".
Teams from the same country could not be drawn together Thursday, and teams from Ukraine and Russian Federation were also kept apart due to ongoing political tensions. All 32 teams get a basic $17.8 million participation fee. "The important thing is Real Madrid".