The Briton leads his German rival by two points with seven rounds remaining but his seemingly unstoppable charge towards a fourth world title has stalled in the last two races, allowing Rosberg to close the gap at the top of the standings.
Rosberg had surged to a 43-point lead over Hamilton at the start of the season before the Briton won six of seven races to seize the momentum going into Formula One’s traditional summer break with a healthy 19-point cushion.
In the two races since the season reconvened, Hamilton did well to surge through the field from the back of the grid to finish third in Belgium but endured a miserable start from pole at Monza as Rosberg romped to a second straight triumph.
A second-place finish in Italy was not a total disaster but Hamilton had dominated practice and qualifying and would have been expected to convert his superiority into a 50th Formula One victory.