Pedro Obiang put the hosts in front after 15 minutes but Udinese turned the match around with first-half goals from Alex Geijo and Danilo.
Substitute Gabbiadini, who according to media reports is set to join Napoli in the January transfer window, headed Sampdoria level on the hour.
Ninth-placed Udinese then had Thomas Heurtaux sent off with two minutes to go.
"At times he has lacked determination," Sampdoria coach Sinisa Mihajlovic told Sky Sports in reference to Gabbiadini. "Having him sit on the bench seems to have given him extra motivation."
Elsewhere, two goals from Polish international Kamil Glik gave struggling Torino a 2-1 home win over Genoa while Palermo chalked up a club record eighth straight top-flight game without defeat by drawing 3-3 at Atalanta.
Alberto Paloschi's late header also handed Chievo a 1-0 victory in the derby tussle with Verona.
Lazio will move back into third spot if they can beat Inter Milan at the San Siro in the evening match.
Juventus, who meet Napoli in the Italian Super Cup in Qatar on Monday, are top with 39 points ahead of AS Roma (36).
Napoli and Sampdoria both have 27 points from 16 games.
(Editing by Tony Jimenez)
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