Gallagher has agreed a five-year deal with Atletico Madrid, who have negotiated a £33million deal with the Blues.
The England international turned down the offer of a new two-year deal at Stamford Bridge as he does not feel the length of the contract reflects his position in the team.
However, it is understood Chelsea made clear to Gallagher that he is not expected to be a regular first-team starter in the coming seasons under new manager Enzo Maresca, with his possession-based style of football.
As a result, Gallagher was banished from the first-team with the club unwilling to allow him to leave on a free transfer next year.
Chelsea had previously accepted a club record bid from Aston Villa for the 24-year-old, but the player turned down the move.
Gallagher has been with Chelsea since he was eight and had four loan spells away, at Charlton, Swansea, West Brom and Swansea, before breaking into the first-team in 2022.
In the last two years, he has chipped in with ten goals and as many assists in 95 games in all competitions.
Incredibly, he missed just four top-flight matches in 2023/24, with no Chelsea player featuring in more matches than Gallagher’s 50 last campaign.
Former Tottenham midfielder Jamie O’Hara believes it will be a huge mistake from Chelsea to let him go.
Reacting to the news that Atletico’s transfer offer was accepted, the talkSPORT co-host said: “I think it’s a disgrace. They’re letting him go.
“He’s a captain of the football club, works his tail off, loves the team.
“Everyone likes him and he gives everything on the football pitch. You’ll never see him go missing on the football pitch.
“What he lacks in quality, he makes up for in heart and desire.
“I think they’re making a mistake getting rid of players like that.”
