Well.. there is always a possibility. Crawford is in his prime and he will pose a very tough challenge to Pacquiao. But I remember the Thurman vs Pacquiao fight, and the same was said at that time as well. A few weeks before the match, Thurman was the overwhelming favorite, with odds ranging from 1.4-1.6. But Pacquiao won the fight despite his disadvantages (with from and age). The lesson is to never underestimate Pacquiao.
I heard the same, there were a lot of concern that Thurman is dangerous for Manny Pacquiao but they are wrong, Pacquiao even fight Thurman toe to toe and you can tell how much stamina he has because even though he was also hit by heavy punches, he still trade punches and was standing until the end of the fight, and win the fight.
The most important thing is that the Pacquiao vs Thurman fight lasted for full 12 rounds, and even then Pacquiao managed to win (and that too by a considerable margin. Both Dave Moretti and Tim Cheatham had Pacquiao winning by 115-112). Before the fight a lot of people were saying that Pacquaio will not last for full 12 rounds and the only chance for him is if he knocks out Keith Thurman. But they were proved wrong.