Karius joined Liverpool this summer from Mainz and has had a difficult start at his new club. Jurgen Klopp has dropped him as the first choice goalkeeper, after their last draw and defeat. Fans have criticized the 23-year-old.
His Belgian team-mate believes Karius will celebrate very soon a perfect comeback.
"That's part of the job and you have to be mentally strong to deal with that," said Mignolet. "I'm coming up to 29, and I've been through it as well. It's not nice.
"You only get stronger from it, especially at a club like Liverpool Football Club. One thing gets really big out of nothing.
We are team-mates, we all have to get through it and push each other. For Loris, it will not be nice. But he's more than capable and professional enough to deal with it and learn from it
"He will only get stronger from it.," he told 'Sky Sports'.