As one of the most condensed domestic football schedules witnessed in the 21st century has finally ended, clubs will now watch their stars compete for international honours. The UEFA Euro 2020 and CONMEBOL Copa America 2020 are both scheduled to kick off in the second week of June.This will also mean that these tournaments will be played during the European transfer window. This summer's window is set to open on June 9, and will go right up until the end of August.Several transfers in the past have happened while players were away on international duty. And, in many cases, clubs have wrapped up deals to sign players even before the transfer window was officially opened.This summer is no different as there have already been a few big-name players whose transfers have been confirmed prior to the transfer window opening. On that note, here is a look at five high-profile players whose transfers have already been made official for the upcoming season.#5 Mike Maignan | Lille to AC Milan | €13mAFC Ajax v Lille OSC - UEFA Europa League Round Of 32 Leg TwoLille have had a phenomenal 2020-21 campaign that saw them win their first Ligue 1 title in a decade, and Mike Maignan had a large role to play in their success. The Frenchman was arguably the best goalkeeper across the top five leagues in 2020-21. He managed more clean sheets (21) and conceded the least number of goals per 90 (0.61) than anyone in Europe.AC Milan announced their capture of Lille's title-winning hero for just €13m, which is an absolute bargain for a player of Maignan's quality.We're in safe hands: M² 🧤 #SempreMilan pic.twitter.com/RSrIO3TZwT— AC Milan (@acmilan) May 27, 2021The former Paris Saint-Germain man will serve as a direct replacement for Gigi Donnarumma. The Italian is set to leave the Rossoneri this summer on a free transfer after refusing their contract renewal offers.#4 Dayot Upamecano | RB Leipzig to Bayern Munich | €42.5mRB Leipzig v 1. FC Koeln - BundesligaDayot Upamecano's future has been a topic of discussion for over two years now. Upamecano has been regularly linked with the likes of Real Madrid, Manchester United, and other high-profile clubs for quite some time. After another impressive campaign at RB Leipzig, perennial Bundesliga champions Bayern Munich ended this speculation by completing a deal for him. The Bavarians announced the defender's signing towards the end of the 2020-21 campaign. Upamecano could be a direct replacement for Jerome Boateng, who has departed from the Allianz Arena.ℹ️ #FCBayern have agreed to sign Dayot #Upamecano from 1st July 2021 🤝📰 https://t.co/h1HtzEKVDG#MiaSanMia— 🏆CHAMPIONS🏆 (@FCBayernEN) February 14, 2021He will join Bayern's growing French contingent, which includes the likes of Lucas Hernandez and Kingsley Coman. The 22-year-old will also reunite with Julian Nagelsmann, the coach at his former club RB Leipzig. Also read: 5 Goalkeepers who could be on the move this summer