World super-middleweight champion Carl Froch has acknowledged that Glen Johnson poses a "serious threat" to his title when they meet this Saturday.
The 33-year-old faces Johnson, 42, in Atlantic City, where a win for either man would see him through to the Super Six final against Andre Ward.
Froch told BBC Radio Nottingham: "It's good I'll be in America for two-and-a-half weeks to get my mind switched on.
"I can't take the wily old fox lightly. He's a serious threat."
The Nottingham-born fighter added: "He's been in with the best of them and has only mixed it at top level so I'm taking it very seriously. I need to get my mind focused."
The winner of the contest would face Ward, who beat Arthur Abraham in the other semi-final earlier this month, with both the WBC and WBA belts on the line.
Froch added: "It has added to the aspiration (against Johnson), but it will have added to Johnson's too. He'll know that if he can try and pull a win off against me, his next fight will be a unification bout.
"But at 42, he knows he's in the last-chance saloon."
The Super Six began in 2009 and originally featured Froch, Andre Dirrell, Arthur Abraham, Jermain Taylor, Andre Ward and WBA champion Mikkel Kessler.
However, the tournament has been beset by injuries, withdrawals and controversy.
Taylor, Dirrell and Kessler all withdrew through injury, while substitute fighter Johnson qualified for the semifinals after only one fight, when he knocked out another replacement, Allan Green.