Manchester City legend Vincent Kompany says the team bus attack by Liverpool fans last year sparked the rivalry between the two clubs.
In April 2018, the coach carrying City's stars to Anfield was bombarded with bottles, stones and flares.
Merseyside Police have assured Pep Guardiola's men they are doing all they can to ensure no repeat at tomorrow's title showdown.
Ex-City captain Kompany, writing in his book Treble Triumph with Ian Cheeseman, serialised in The Sun, said: “I was on the coach as it was bricked. That moment things changed.
“The rivalry increased and they became our No 1 team to beat. The mood among City fans towards these games against Liverpool had changed.
“They'd always been seen as tough fixtures but now there was more tension."