Porto - Besiktas managed to break through FC Porto's defence to open its Champions League campaign with a 3-1 win on Wednesday.
Porto was yet to concede this season, but Talisca, Cenk Tosun, and Ryan Babel all scored for the visitors at Estadio do Dragao.
After Talisca opened the scoring, Porto equalized thanks to an own goal by Besiktas defender Dusko Tosic.
Tosun gave the Turkish side the lead again before half-time, and Babel sealed the victory in the second half.
"It was a great game from us, defensively as well as in attack," Talisca said. "We did exactly what our coach asked of us and everything worked out well. We had a very good first half, while Porto dominated us somewhat in the second but we knew how to stand up to that."
In the other Group G match, Leipzig made its Champions League debut with a 1-1 home draw against Monaco.
Porto has won only two of its last eight home matches in European competitions.
It was coming off five straight wins to start the season in Portugal, all without conceding.
Porto was without Vincent Aboubakar and Maxi Pereira because of suspensions. Aboubakar played on loan with Besiktas last season.
"We had enough chances to have ended with a different result," Porto coach Sergio Conceicao said.