Brazilian Hernanes scored twice while Giuseppe Biava and Tommaso Rocchi also got their names on the scoresheet as Rodrigo Palacio and Antonio Floro Flores replied for the visitors at the Stadio Olimpico yesterday.
Lazio moved temporarily at least above Udinese into fourth place but the northerners could reclaim their two-point advantage if they win at Chievo on Sunday.
It means Lazio have also piled the pressure on neighbours Roma who will have to win at Catania to keep pace with their city rivals. Hernanes said his team had done there bit and now it was up to the others.
"We fulfilled our commitment and now we'll wait and see how tomorrow (Sunday) goes and after that we'll think about the Champions League. After three defeats in a row we had that hanging over us when we started the game,"he said.
"We were down and weren't managing to give 100 percent but then we spoke at half-time to change the spirit of the team and that's what happened."
Coach Edy Reja said his team had needed a kick-start following their losses to Inter Milan, Juventus and Udinese.
"There was some disappointment during the week because there was the fear that we wouldn't achieve our objective of qualifying for the Champions League, but we have to believe," he said.
"At half-time I said if we kept playing like that we risked throwing away an entire season. The players reacted, they were committed and I congratulate them", he added.
"We have to believe right to the end. We've done what we had to do and I hope today's win will inspire us. We have 63 points and we hope that at the end we'll have at least qualified for Europe."