The 45-year-old expressed his delight at the resurgence of his side following its disastrous start to the campaign.
A double from Giampaolo Pazzini and a Kevin-Prince Boateng strike sealed the victory against the Biancocelesti - who had Antonio Candreva sent off in the first half - with Milan leapfrogging the visitors into third spot.
"The team deserves to be in third place, as they are playing well," he told reporters after the game. "We must remember to stay focused in our fight for Europe. These days we are more organized as a side, which makes it easier to win.
"We're in good shape, and I hope we can continue this way until season's end. We've got to concentrate on achieving this objective."
Lazio boss Vladimir Petkovic admitted the San Siro side was now favorite to qualify for the Champions League, but felt the club was aided by the performance of the referee.
"Milan are the team to beat, but from the 16th minute [when Candreva saw red] onwards, it was to be a totally different game. When people complain about referees, I hope they don't forget us," he said. "As happened against Fiorentina, again we paid the price for certain decisions. While these things happened, we might have been on a par with Milan at full strength.
"I have to compliment my team however, as they tried to give their best till the end."