Pompey's attacking talent once again took centre stage in Saturday's 3-1 success over the Black Cats.
Curtis produced a goal and through ball for Oli Hawkins, who was brought down by Glenn Loovens for a penalty and red card in the game's key moment.
The 22-year-old's 53rd-minute strike came seconds after he was given a yellow card for a high challenge on Max Power which had the visitors appealing for a dismissal.
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Ref Peter Bankes was happy to issue a caution, however, paving the way for the Irishman to bag his eighth goal of the season.
Curtis said: '˜I tried to go for the ball, but the ref has seen it a different way.
'˜You will get them in games where the ref thinks you've dived in rashly.
'˜You take the yellow card in those situations and get on with it.
'˜Then after that it goes my way (with the second goal).
'˜I've been practising with my left and getting stronger with my left foot.
'˜I've been practising going both ways and if you have that in your locker it can put off the defender.
'˜I'm more than capable of doing that and I've shown that a couple of times this season with goals I've scored.'
Curtis was relieved to see a mix-up between him and Lee Brown for Sunderland's goal count for little in the final reckoning.
That allowed Luke O'Nien to make it 2-1 in a frenetic period, before Ben Thompson effectively settled the game in the 63rd minute.
Curtis added: '˜It was a mixed communication between me and Browny.
'˜I've shouted to him but he didn't hear me.
'˜You are going to get these moments sometimes, but I'm just glad we got the result in the end.'
New Republic of Ireland manager Mick McCarthy was at Fratton Park to see Curtis shine, and the summer signing from Derry City is hopeful he made a strong impression ahead of European Championship qualifiers in March.
Curtis said: '˜I've spoken to Mick McCarthy and he was at the game.
'˜He's a nice fella and hopefully he's seen something he likes in me.
'˜If you want to be the best player you can be and play international football you need to show the manager what you can do and what you have in your locker.'