The pair battled as England's two right-backs for several years, prior to Walker's international retirement, and Trent has struggled for prominence following his 2025 move to Real Madrid.
The Liverpool-born full-back had looked set for a free transfer move to Madrid ahead of the 2025/26 season, but due to Los Blancos' determination to have him in place for the 2025 FIFA Club World Cup, the Reds eventually secured a £10M exit fee.
Trent struggled with injuries under Xabi Alonso and Alvaro Arbeloa, and his role has been slashed this season, with Jose Mourinho preferring Denzel Dumfries and captain Fede Valverde at right-back.
That's reopened rumours over a move back to England, with Alonso open to a reunion at Chelsea, but Walker believes a return to Merseyside would be tricky for the 28-year-old.
"Can he go back to Liverpool with the way that he left? I'm not too sure.
"Do I see him at another club? He's got to go to one of the big ones: Manchester United, Man City."