Irvine's men went down 3-1 at the Hawthorns to record their third successive pre-season defeat, with a brace from Jackson Martinez proving the difference between the sides.
Speaking to his club's official website after the loss, Irvine was full of praise for West Brom's Primeira Liga opponents, claiming they would be a match for any team in the English top flight.
"It was an extremely tough game against a fantastic team. I'm not sure we'll play a better team this season," said the Scot.
"They controlled possession, they pressed really well when they didn't have possession and they passed the ball extremely well. I'm not disheartened because we don't expect to come up against that every week.
"Obviously we can pass the ball better, and that's something that the players recognise, but it's very easy to sit in the stand and think we could pass the ball better when you've been under that kind of pressure."
West Brom kick off their Premier League campaign against Sunderland next Saturday and Irvine bemoaned the injury problems that have hampered his close-season preparations.
"We've probably got eight players who aren't in the right condition to start, but we'll have to include some of them," he added.
"We have got some work to do in the next week, and we'll look to being fully prepared for the Sunderland game. But I don't expect Sunderland, with all due respect to them, to be as good as Porto."
Irvine could at least take heart from the returns of captain Chris Brunt and forward Stephane Sessegnon, who have each missed large chunks of pre-season through injury.
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