The Nerazzurri were leading 1-0 in Catania before letting in two goals right after the restart.
"We needed to pick up points and had been achieving that, but after the break conceded two counter-attacks straight away," Ranieri.
"We should've stayed united and solid, as we were in the first half. Now we've got to stay calm and continue working, because there's a lot to do.
"I had asked the team to keep their shape. Now we want to react and climb back up the hill."