El Toro bagged a brace in Sardinia after the opening Matteo Darmian looping header, while he also forced great saves and struck the frame of the goal.
That 3-1 victory keeps the title race open to the final round, because the two-point gap remains.
As Milan have a superior head-to-head record, it means that the Rossoneri need only a point to guarantee the Scudetto when they travel to Sassuolo.
Inter, meanwhile, host a Sampdoria side who are already safe from the drop.
“It was a difficult match, as Cagliari had so much at stake too, but we needed to win and I am happy we did it,” Lautaro Martinez told DAZN.
“Now we have to win the final match and hope for the best. We still have a possibility of winning the Scudetto and therefore we believe.”
When asked about his regrets for the season, Lautaro did not choose the 2-1 defeat to Milan that effectively divides the teams, but rather a different loss at the Stadio Dall’Ara.
“Unfortunately, we dropped very important points against Bologna. If I had the chance to replay one game, it would be that one, that was a real shame.”
That 2-1 defeat was the rescheduled Week 20 game that was moved from January to May after Bologna were hit with a COVID-19 outbreak, forcing them to postpone the fixture.
Lautaro Martínez has put this game to bed with the finest of finishes 🤤
What composure to dink the ball over the keeper this late in the game.
The Serie A title race is going right down to the wire! 😅 pic.twitter.com/uVQT5Q5BS8
— Football on BT Sport (@btsportfootball) May 15, 2022