Satpayev completed his move to Stamford Bridge on his 18th birthday this week, signing a six-year contract with the option of a further year, before immediately being loaned to the newly relegated Clarets for the season.
The Kazakhstan international's transfer had been agreed as far back as February 2025, when Chelsea moved for around €4m to beat other European clubs to his signature — a deal that set a transfer record for the Kazakhstan Premier League.
He joins Burnley with 58 senior appearances and 26 goals for Kairat already to his name, having become the third-youngest player ever to score in the Champions League last season at 17 years and 106 days old.
"I'm very pleased to be here," Satpayev said. "It's a great opportunity for me in my career and a great club to show what I can do and help the team get back to where they belong. It's my first time playing in England and I'm ready now to take on the next chapter and have a successful time with Burnley."
Kavuma-McQueen, 17, moves to Portsmouth having made one senior appearance for Chelsea, in a 7-0 FA Cup win over Port Vale, and having signed professional terms in January. He was involved in Chelsea's Champions League squads against Paris Saint-Germain and Ajax last season and made the matchday squad for Premier League games against Liverpool and Tottenham, without playing, after progressing through the club's Under-18s and Under-21s.
Portsmouth boss John Mousinho said the winger, who can play on either flank, had been closely tracked.
"We've been in the market for wingers for quite a while and Ryan ticks all the boxes of the profile of player that we want to bring in," Mousinho told BBC Radio Solent.
"He's quick, direct, can play off both sides and he's only 17 so that probably tells you how highly we rate him and how highly Chelsea rate him. He was away with the first team this pre-season and played minutes out on their tour.
"We've tracked him throughout his youth career and he made the step up last year into the 21s side so we're really excited to get him through the door."
The two moves are part of a busy week of outgoing loans at Chelsea, with Reggie Walsh joining Wigan Athletic and forward Shim Mheuka also closing in on a departure, as the club continues to manage a squad heavily stocked with academy talent following its recruitment strategy in recent transfer windows.