The Champions League-chasing side from Bergamo had won their last two home games against AC Milan and Parma with 5-0 scorelines each time.

But they slipped up against SPAL who snatched just their fourth win of the season to move off the bottom of the table.

Gian Piero Gasperini's side missed the chance to climb above Roma into the final Champions League place, and are now three points behind the side from the capital in fifth.

Slovenian forward Josip Ilicic put Atalanta ahead after 16 minutes with a clever back-heel flick beating Etrit Berisha in the SPAL goal.

But Petagna pulled SPAL level after 54 minutes by scoring his fifth goal in four meetings against his former club.

Mattia Valoti snatched the winner six minutes later with new signing Bryan Dabo playing a role in the goal on his first start for SPAL.

Colombian striker Duvan Zapata missed chances to equalise for the hosts following a long injury layoff as Atalanta fell to their fifth defeat of the season and fourth at home.

Gasperini had conceded that his players were suffering from fatigue after their surprise elimination from the Italian Cup by Fiorentina.

Atalanta are playing their first season in the Champions League and host Valencia in the last 16, first leg at San Siro on February 19.

Champions Juventus beat Parma 2-1 to open up a four-point advantage on second-placed Inter Milan who were held 1-1 at promoted Lecce on Sunday.

Lazio are third, a further two points behind with a game in hand, after hammering Sampdoria 5-1 on Saturday.

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