Danny Drinkwater has submitted a transfer request to Leicester, Press Association Sport understands.
The midfielder, 27, is a transfer target for Chelsea amid manager Antonio Conte's pursuit of a replacement for Nemanja Matic.
Last summer he signed a new contract to commit his future to the club until 2021, but having acted could yet force a departure before Thursday's conclusion of the summer transfer window.
As well as a return to Champions League football, a potential transfer to Chelsea would reunite Drinkwater with N'Golo Kante, his central midfield partner when Leicester won the Premier League title in 2016.
The present champions have already recruited Tiemoue Bakayoko from Monaco, but their pursuit of the England international follows the departure of Nathaniel Chalobah to Watford and Ruben Loftus-Cheek's loan to Crystal Palace.
It is because of their strength in depth, however, that former Chelsea player Ray Wilkins believes Drinkwater would be wrong to move to Stamford Bridge.
Conte also has Cesc Fabregas as a further option in central midfield, and Wilkins told Talksport: "Danny has done really well over the last couple of years.
"The important thing again is to play. If Danny comes to Chelsea, (Tiemoue) Bakayoko has cost £40million, Kante everybody loves.
"Is he going to get a game with Fabregas as well? If I was Danny I'd go somewhere where I would play, personally."
Drinkwater joined Leicester from Manchester United in 2012, and has since played for England three times.