Marco Silva's men had been looking to kick-start their campaign after drawing their league opener at Academica a week earlier and the morale-boosting triumph they craved arrived in second-half stoppage time.
Nani, who was greeted with a rapturous welcome, made his second debut for his boyhood club after he returned on loan from Manchester United as part of Marcos Rojo's move to Old Trafford.
There was no such late panic for Porto, though, as a 1-0 victory at Pacos Ferreira continued Julen Lopetegui's winning start in charge.
The change did not prove to be particularly detrimental, however, as Tello's replacement Juan Quintero set up Jackson Martinez for the only goal of the game in the 40th minute.
Rui Pedro's 83rd-minute goal gave the hosts something to worry about late on but in the end they had already done enough.
A quick-fire double at the beginning of the second half from Fransergio and Moussa Maazou initially opened up a two-goal advantage and they held on for a narrow victory, a first for new coach Leonel Pontes.
