The visitors made a bright start and took the lead in the sixth minute when Darko Lazovic raced to the byline and pulled the ball back to Leonardo Pavoletti who arrived at the front post to slot past the keeper.
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In the 31st minute the hosts were rewarded for their pressure as Leonardo Blanchard volleyed an overhead kick into the top corner, despite lying on the ground as he struck the ball.
Genoa were dealt another blow five minutes later when De Maio was giving his marching orders for picking up two yellow cards in quick succession.
The Canarini quickly made their numerical advantage count as within two minutes Blanchard's free kick deflected kindly into the path of Modibo Diakite, who fired in from close range to give them the lead.
Despite playing with a man less, Genoa pressed forward in search of an equaliser and Lazovic came within inches of scoring when his free kick struck the bar.
However, with 15 minutes left to play the visitors hauled themselves back on level terms as Serge Gakpe arrived at the back post to turn in Lazovic's low delivery across the six-yard box and earn his side a point.