After picking the ball up from Belenenses top scorer Carlos Martins, Ruben Pinto watched as his shot from outside the box went narrowly wide of the Poznan goal.
The home side continued to push for a goal, with Denis Thomalla watching his shot from distance pass wide of the post and Dawid Kownacki having an attempt blocked.
Belenenses midfielder Miguel Rosa headed the ball over following a Carlos Martins corner with just over 10 minutes remaining in the half, and hit the crossbar with a second header shortly after.
Shortly after the half-time break, Gergo Lovrencsics saw his shot go wide of the target for Poznan before Martins struck the post after being set up by Andre Geraldes.
Formella and defender Paulus Arajuuri both had half-chances for Poznan with less than 30 minutes to go, before Belenenses stopper Ventura was required to save shots from Szymon Pawlowski and Formella again.
Karol Linetty had another Poznan chance from outside the box with 10 minutes to go, but watched his shot fly over the bar.
Belenenses had two chances to grab a winning goal in stoppage time, but both Rosa and Kuca hit shots wide of the posts to seal a stalemate.