The Oxford United manager believes his defence faced their toughest challenge of the season against Kenny Jackett’s forward line.
And Robinson admitted his midfielder Cameron Brannagan should have been sent off in the U’s 1-0 defeat at the Kassam Stadium - although Ronan Curtis should have walked too.
Pompey have struggled for goals from their attacking options in recent weeks, but that hasn’t stopped the Scouser lavishing praise on their quality and problems they present.
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He told BBC Radio Oxford: ‘Portsmouth’s front four is as good as you’re going to get in this league.
‘That’s the hardest challenge a back line will have.
They have so much versatility, pace and power.
‘We stood up to that relatively well.
‘I thought their intensity in the second half and their strikers made it very difficult for our centre-backs.
‘Our centre-backs dropped deeper, their back line pushed a bit higher and for 25 minutes they were the better team.
‘It was a fantastic cross and a great goal.
‘Then for the last 15 minutes we chucked the kitchen sink at them and probably had the best two chances of the game to take a point.
‘Then you’d take a point and say that’s what happens against Portsmouth.’
Robinson felt his side were fortunate not to see Brannagan dismissed for swinging a forearm at Marcus Harness in the second half.
He added: ‘It was a blatant penalty on Sam Winnall but Cameron is probably lucky to get away with the trailing arm.
‘You have to be honest in those situations. I think Harness has kicked out and then Cameron swung an arm and caught him. It was something the referee missed.’
There was plenty of debate over whether Ronan Curtis should have also been sent off for a string of infringements before being withdrawn for John Marquis.
Robinson felt that should have been the case - but there was also praise for the Republic of Ireland international and ref Graham Salisbury.
He said: ‘Curtis is what he is.
‘The tackle is a bad tackle and he did pull back, so it is a booking
‘The referee said it probably was a booking if it was 30 yards higher up the pitch. I get that.
I thought the referee had a good game.
‘I can moan about the penalty and they can about the Brannagan thing and what the ref didn’t see.
‘I thought his experience and the way he managed the teams was calm and you generally don’t see that at this level.
‘Curtis always plays on the edge and there was a reason they subbed him, but he’s a good player.’
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