The last time was Manny Pacquiao, wo is supposed to face Spence but suddenly was replace by Ugas and obviously, Manny lost that fight already.
That was not the reason, whoever trained or coach Manny, he would not won in that fight because he said he has cramps on his legs that bothers him in the fight since he cannot use his quickness. Sometimes, boxers losses, it's just up to them how they'll recover from that loss.
It wasn't the whole reason why Pacquiao lost the fight against Ugas but I still believe that part of that reason why he lost is the sudden change of opponent which is Ugas because Spence can't fight because of the tear in somewhere in his eyes. That sudden change is a factor why Manny has lost because majority of the preparation he did was for Spence while Ugas was already training for Pacquiao if in case Spence can't make it, and it did happen.