Benassi almost found the breakthrough for his side in the 27th minute as he raided forward to the edge of the box and drilled his strike towards the bottom corner, but Sa made another impressive stop to keep the strike out.
In the second half, Italy came inches away from taking the lead when Belotti met a cross from the left wing and headed at goal, only to see his effort clatter off the crossbar and bounce clear.
The Azzurri kept the pressure on Portugal and they came close minutes later as Berardi fired a low ball across the face of goal towards Benassi, but the midfielder just couldn't make contact, which would have led to a certain goal.
Belotti should have put Italy ahead in the 71st minute after he could only guide his effort from close range past the post when latching on to a pinpoint cross from Davide Zappacosta from the right wing.
Rui Jorge's men almost broke the deadlock when a loose ball fell to Iuri Meideros at the back post and he drilled a volley low towards the bottom corner, but his shot was well saved by Francesco Bardi.
Cristiano Biraghi could have won the game for the Azzurri in the dying seconds when he was played through down the left, but his touch was heavy and it allowed Sa to smother the ball at his feet.