Boselli's goal on 96 minutes ensured a dramatic ending after the match seemed headed for a 1-1 draw at the Marassi, following earlier strikes from Floro Flores and Pozzi
Antonio Floro Flores latched onto a corner just before half-time to open the scoring against the run of play. However, Nicola Pozzi struck after the interval when he tapped in a fumble from close range as Eduardo spilled a shot and looked to have dropped for his side. However, Mauro Boselli won it with the last kick of the game.
The game was significant, perhaps, more than ever for Sampdoria as they came into battle struggling in the relegation zone. Genoa, however, had also been suffering from a mediocre season.
Alberto Cavasin's men showed good early signs as they tried to make inroads from the start. Stefano Lucchini made an effort to head the ball as it was flashed across the box, but Kakhaber Kaladze defended well.
Despite struggling, the Blucerchiati were eager to revive survival hopes and Daniele Mannini showed good vision to spot Angelo Palombo's run on the edge of the box. He fed the Italian who went close as his shot cleared the bar.
Genoa continued to press in a direct approach though and Rafinha got his head down and drove forwards, but his shot was dragged wide of goal. As expected, things were cagey, nervy, and the tension in the stands raised the climate.
Floro Flores had few options up front, and so his tame shot was saved low by Da Costa who got a rare start as Gianluca Curci watched from the bench. There was stiff resistance from both teams, with chances limited at both ends.
The Grifoni should have done better when Floro Flores crept in behind following a good break, but he failed to find the target as he sent his effort into the stands. Down the other end Eduardo was forced to scramble clear a Mannini cross-shot which caused problems.
Rodrigo Palacio tried his best to scuttle open a corridor for chances, but route one football from the Grifoni proved ineffective as Costa enjoyed catching practice.
Deadlock was eventually broken when Floro Flores headed into the back of the net after Palacio knocked the ball on from a corner on the stroke of half-time. It was harsh on Sampdoria as they were caught napping.
The second-half started without many highlights for Sampdoria, but actual sparks did fly eventually, because Genoa fans lit a flare behind goal. Smoke billowed up and around the Marassi, forcing the game to grind to a halt momentarily while the air cleared.
Jonathan Biabiany had the best chance to get Samp back on level terms. His pace saw him first to Pozzi's cross, but the header flashed wide of the upright. He was the dangerman for the struggling side, but a combination of slack finishing and lack of belief saw Genoa cope well under increasing pressure.
However, the Grifoni's resistance was soon blown apart from Pozzi as he tapped home a lose ball when Eduardo shockingly dropped a Palombo shot from range.
Tempers flared toward the end as Genoa ended the game with 10 men: Giandomenico Mesto was sent off for an elbow on Palombo.
The match had an even more wild finish though, Boselli making it 2-1 in the sixth minute of injury time when he turned Lucchini and stuck the ball home to win maximum points.