Alexander Kerzhakov's 86th-minute winner was enough for Spalletti's side in Portugal, but the Italian preferred to deflect the praise to his Brazilian forward after the game.
"Hulk was the player that gave them the most problems," Spalletti told reporters after the game.
"He was everywhere, dribbling from the right, providing Kerzhakov with the goal. He was crucial in our win."
Hulk spent four years with Porto before he moved to Russia in the summer of 2012 for around £40m.