Francesco Farioli saw his FC Porto side settle for a 1-1 draw against Nottingham Forest on Thursday night after failing to turn early dominance into victory.
The second leg will take place in England next Thursday.
Porto nearly made the perfect start within the opening minute when Terem Moffi found himself unmarked on the edge of the area, but he dragged his shot wide before Stefan Ortega cleared the danger.
The home side eventually took the lead soon after. Pablo Rosario produced a neat backheel to send Gabri Veiga through, and his delivery across goal was finished at the back post by William Gomes.
However, Porto’s lead disappeared almost immediately. Defender Martim Fernandes attempted to head the ball back to goalkeeper Diogo Costa from long range, but badly misjudged it and sent the ball into his own net to make it 1-1.
Fernandes’ difficult evening got worse moments later when he suffered an injury and had to be replaced by Alberto Costa.
Both teams had chances after the break. Nottingham believed they had completed the turnaround through Igor Jesus, but the goal was ruled out after a foul on Diogo Costa.
Porto pushed hard in the closing stages in search of a winner. William Gomes tested Ortega again, while Viktor Froholdt fired narrowly wide from inside the penalty area, but the Portuguese side had to settle for a draw.
