Milan went into Sunday's game at the Stadio Olimpico on the back of three consecutive Serie A defeats, a slump in form that has caused unrest at San Siro to the point that head coach Seedorf and his players have spoken to the club's demonstrating Ultras in recent weeks.
And it looked as if the weight of pressure was easing on his beleaguered side when Milan took the lead just before half-time in fortuitous circumstances after Kaka's cross deflected off Lazio's Abdoulay Konko before finding its way into the near corner.
Indeed, had Keisuke Honda headed in a fantastic cross from Kaka just before half-time, it may have pushed the visitors on to the victory they badly needed.
But Edoardo Reja's side put in a spirited second-half performance and Lazio got their rewards when Gonzalez reacted quickest to instinctively head home just after the hour.
Substitute Mario Balotelli was denied by the frame of the goal late on as Lazio extended their unbeaten home run in the league against Milan to four games, with Seedorf's men wedged in the bottom half of the table.
Both sides were without their first-choice goalkeepers, with Christian Abbiati suspended and Federico Marchetti ill, so Marco Amelia and Etrit Berisha deputised.
Seedorf has been in the spotlight after the club's recent UEFA Champions League elimination coupled with poor league results and all Milan had to show for their early endeavours was a wild long-range effort from Honda that flew over.
Lazio had the ball in the net just before the break when Diego Novaretti's header squirmed under Amelia, but it was ruled offside as Giuseppe Biava challenged for the ball when coming back from an offside position.
And fortune favoured Milan again two minutes before half-time as Seedorf's men took the lead in fortunate circumstances when Kaka's left-wing cross deflected off Konko, wrong-footed Berisha and nestled in the net.
It should have been two in first-half injury time when Kaka's wicked delivery found Honda 12 yards out, but he ballooned his header over with the goal gaping.
Lazio were looking to avoid a second consecutive home defeat and showed signs of life early in the second half when Balde Keita forced a save from Amelia.
And Lazio were level after 61 minutes when Gonzalez showed great anticipation to react to Lucas Biglia's flick-on to bury a bullet header past Amelia.
Seedorf responded by bringing on Balotelli and he almost repaid his manager, but his thunderous 20-yard drive cannoned back off the post with Berisha beaten.
