Vickers established himself as first-choice goalkeeper in January, and since then has only missed games in the Football League Trophy. He might have played in the final, but a broken hand saving a shot in training spared Warne a difficult decision.
He has always maintained there is little to choose between Vickers and Johansson, who put in some excellent performances during last season's Championship relegation run-in, and he is not changing his tune now but he did acknowledge it makes his life more difficult.
"I can flip a coin on both of them, it doesn't bother me which one plays, it's just the fact it's more stressful if something happens to Vik," he commented.
"We have emergency loans in place - well, I say in place, names, but they change on a weekly basis anyway because they might get taken by someone else.
"It adds a bit more sugar to the spice."
Rotherham's third-choice goalkeeper is Josh Chapman, signed from Sheffield United in the summer but yet to make a senior appearance.
They are only two points behind the Dons with two games in hand, three behind Wigan on the same games played. Rotherham host Charlton Athletic on Saturday.
Vickers is expected to be out for two or three months, which should mean he is back for the start of pre-season.
On his injury, Warne said: "He's out for the season. His hand's in plaster, he broke a bone making a save in training.
"It could have been a lot worse, it could have been nine months, which would have been horrendous.
"We did have a slight glimmer of hope they might be able to do something but I never really bought into that - a goalkeeper can't have a broken hand and play on!
"It's a big miss and I feel for him because he's been excellent - as has Viktor."