Much of the animosity between Chelsea's Frank Lampard and Liverpool's Xabi Alonso stems from a challenge in 2005 which left the Spanish international with a broken ankle. The England midfielder admits he was in the wrong and phoned Alonso after the game to offer his apologies, but the pair have not seen eye-to-eye since.
Lampard told the Daily Mail: "It is strong, I can't deny that. The players feel an extra edge. You'll see it on Sunday. There is respect between the teams, though. Steven Gerrard always says how hard it is to play against us at our place and it is the same up there.
"Just a sea of red shirts on the pitch at times because they work so hard and put you under so much pressure. They are a horrible lot like that.
"We've played them so many times in big games so lots of individual tensions build up. There is always something between me and Xabi Alonso, for instance."
Lampard said: "It was a foul and I got booked, so I am not trying to plead innocence, but it was a tap, it wasn't anything nasty; the sort of tackle that happens all the time, both ways.
"That night, when I heard how it had worked out, I felt very bad and phoned to apologise but he wouldn't really have it and ever since he has that look in his eye when we meet, and there is always a bit of jostling and shoving."