After falling behind 13 minutes from time at the Estadio da Nora, the Tigers hit back with Campbell levelling things up before Jon Toral’s late penalty won it at the death.
“It was a decent workout for everyone involved and it was pleasing to come away with the win,” Campbell said.
“We did our research on them and we knew they had some very good players. They looked sharp, fit and strong – it was a good test which is exactly what you want at this stage.”
Reflecting on his goal, Campbell added: “Pre-season is all about getting your match sharpness back but scoring a few goals is never a bad thing for your confidence when you’re a striker.
“It’s vital for every player to have a good pre-season campaign in order to set you up nicely for when the competitive action gets underway. Hopefully, I can do that this year.”