The U's fought from behind to beat Shrewsbury 3-2 on Saturday to stay just a point behind Pompey with one match remaining.
Oxford, who beat the Blues on penalties in last season's play-off semi-finals, host Burton Albion for their season finale next Sunday.
They've got to win and hope that Pompey drop points against Accrington.
Meanwhile, fifth-placed Blackpool still need a point from their last two games to seal a play-off spot and eight-placed Charlton still harbour ambitions of going up.
And Robinson is relishing the razor-tight battle for the final Championship spot.
He told BBC Oxford: ‘Roll on next Sunday and the balls start rolling again.
‘Charlton will have to score an awful lot of goals to go above us with their game in hand. Depending on Blackpool's result on Tuesday, we could go ahead of them on the last day of the season.
‘If Blackpool don't win and there's four of us fighting for two spots, it's going to be a right ding-dong on the last day of the season.
‘I don't sit here and play games, we just love what we're doing and our job.
‘To get to the last day of the season, to get so close, get to 74 points - that's been enough for many years. Even 72 points is enough so to get the points tally we have is exceptional.
‘We're in it. It was hard and it was tense (at Shrewsbury). It would have been another special moment because this could be a pivotal moment in our history.’