Kevin MacDonald told Total Film that Tatum's discomfort made the final scene more believable, after boiling water was accidentally poured down his wetsuit.
"In some ways it did me a favour because what I was trying to do in that section was break him down," explained MacDonald. "But Channing's such a bulk and so strong and capable that it's very hard to make him feel like he's reached the end.
"He could hardly walk but it was good because it meant that when he was fighting in the final battle he was in pain and couldn't do it very well."
Tatum described the injury as "unbelievably brutal" but said that there is no lasting damage.
"There's no scars or anything," said the actor. "I remember the medic saying, 'I know it's no consolation now, but it's a good thing it hurts because it means there's no nerve damage.'"