Former British boxer Johnny Nelson believes Tyson Fury will pull out of his scheduled rematch with Oleksandr Usyk and could even retire from boxing early in a worrying message for Anthony Joshua. Fury lost his undefeated record last month in the undisputed heavyweight title bout with Usyk. The 35-year-old went into the fight as the bookies favourite and appeared in control at the halfway stage, but Usyk turned things around spectacularly and came close to knocking his opponent out. The Ukrainian was crowned the undisputed heavyweight champion via a split points decision, which Fury felt was un…