Substitute Keita Balde Diao scored his first Serie A goal of the season in the 80th minute to help Lazio remain perfect at home with a 2-0 win over Frosinone on Sunday.The Spanish forward controlled Filip Djordjevic's pass in the box and fired a right-footed shot that hit the far post before finding the back of the net.Frosinone had been close to breaking the deadlock in the 66th minute but Leonardo Blanchard's header struck the crossbar.Lazio doubled their lead at the death when Frosinone goalkeeper Nicola Leali kept Felipe Anderson's lobbed attempt out but only as far as Djordjevic, who tapped in the rebound.ends