The Blues boss opted to employ the former Bradford forward in a wide left position ahead of the Republic of Ireland international in the thrilling win 3-2 win at Adams Park.
Curtis, 23, recovered from a freak injury to feature front the start as Pompey beat promotion rivals on penalties at Wembley.
But the winger delivered a below-par performance and was replaced by Evans early in the second half.
Jackett felt the former Fleetwood forward’s impact off the bench against the Black Cats warranted his place from the start at Wycombe.
Curtis did come on to replace Evans on 84 minutes at Adams Park but Pompey were clinging on to their 3-2 advantage in the dying seconds.
And Jackett explained the reasoning behind the Republic of Ireland international dropping to the bench.
He said: ‘I decided to carry on from where we finished at Wembley.
‘Gareth Evans came on and did so well in a wide left position and Oli Hawkins came on as a centre-forward (against Sunderland).
‘They were both very good I thought at Wembley and deserved their starting places on the back of that.
‘It’s going to be difficult to play the same 11 through the season.
‘Particularly with the length of our season, which is something I spoke about before.
‘Everyone is going to have to face competition.
‘We’re Portsmouth Football Club and there should be good players waiting to come on or waiting to come in should people get injured or form suffer.’
But Jackett believes the influential winger will return to his best form in Pompey’s final six matches.
The 23-year-old’s maiden season in English football has been outstanding.
Curtis has netted 11 goals and added eight assists in League One this season.
And the Blues boss insisted the winger took his Wycombe omission in the ‘right way’.
He added: ‘The injury has upset his rhythm slightly.
‘But that can happen with injuries.
‘I’ve been pleased with his attitude and application to get over that.
‘Ronan has taken it the right way.
‘He has been a regular player.
‘We know he will be back and back to his best after his finger injury.
‘I’m sure he’ll resume what has been a very good debut season for Portsmouth.’