Blues boss Carlo Ancelotti has made the Argentina ace his top target of the transfer window and is ready to launch a bid now in case he is unable to move in the summer.
Ancelotti was happy to wait until the end of the season but realises he has to move in January while the club can still sign players after their transfer ban was suspended.
To ensure that Atletico agree to a deal, it has even been suggested that Chelsea will sign Aguero and then loan him back to the La Liga outfit for the rest of the season.
Ancelotti could even be planning a transfer spree with Franck Ribery and Alexandre Pato also said to be on his list of targets.
Middlesbrough climbed into the Sky Bet Championship play-off positions as Patrick Bamford's first career hat-trick secured a comfortable 3-0 win over Leeds.
Louis Longridge and Greg Docherty will leave friendship at the side of the pitch for 90 minutes on Sunday when Falkirk face Rangers at Ibrox.