David Haye says his comeback could last only one fight if his efforts do not give him the confidence needed to become a world champion again.
Haye, 35, faces Australia’s Mark de Mori on Saturday in his first fight for three-and-a-half years.
He said: “I’m not going to do this if I don’t believe I can win that title.”
Haye won the WBA heavyweight title in 2009, lost his belt two years later to Ukraine’s Wladimir Klitschko and retired in 2013 with a shoulder injury.
Haye’s last fight saw him beat fellow Briton Dereck Chisora at Upton Park in 2012.
Haye, who is expected to beat De Mori, 33, said: “If I’m in there and it feels so far away from me then that will be a consideration [to retire again], even if I win the fight.
“Unless I’m 100 per cent confident I can beat somebody, and become world champion, there’s no point getting in the ring.”
Haye said he would know if his abilities were on the wane, and added: “I’ve boxed for long enough to know that if I’m getting hit with shots I don’t normally get hit with. That’s a tell-tale sign.”