Massimiliano Allegri was sacked on Monday with the European giants sitting 11th in the Serie A - 30 points behind league leaders Juventus.
Former Milan midfielder Clarence Seedorf is expected to take over after retiring from professional football on Tuesday.
Tassotti, in charge for Milan's Coppa Italia clash against Spezia on Wednesday, said everyone needed to take responsibility for the dreadful position Milan were in.
"We're all angry, very angry. At the end, it's the coach who pays for everyone, but it's everyone's fault, the technical staff included and me included. We're surely all responsible for the situation," he said.
"But now it's too late, the fat is in the fire. We had so many chances, the club gave us chances to change as much as they could, but then it was inevitable.
"There's nothing much to do when such things happen mid-season. The choice has been made, now we need to turn over a new leaf, trying to win again, starting tomorrow night."
Assistant coach Tassotti felt he deserved an opportunity to lead Milan - even if only just for one encounter.
"It's a particular moment for everyone here at Milan. It seemed logical to me and fair to be ready to be Milan's coach, even just for a game," he said.
"I've been here for 34 years and I'm obviously always ready to help."
Tassotti intends to play a full-strength Milan team against the mid-table Serie B side as the clubs look to move into the Coppa Italia quarter-finals.
"We're going through a difficult period, that's for sure, but everyone has clear in their minds that tomorrow's game is very important," he said.
"It's important to start well this new stage of the Coppa Italia and the Serie A return leg on Sunday, as we try to move up the table.
"But there's no point in repeating what we've been saying over and over again, we need results."
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