O'Brien's opening spell eight over spell at McLean Park will be remembered as one of the memorable moments of a 22-test career which ends on or before Tuesday.
At one stage he singlehandedly had Pakistan in disarray with his right arm pace - after five overs he remarkable figures of four wickets for three runs.
Pakistan could not score of his first 24 deliveries, by which time Faisal Iqbal and Mohammad Yousuf had come and gone.
Umar Akmal and Misbah-ul-Haq were the other coveted scalps before lunch, but unfortunately he could not claim one of the last five wickets to fall - and missed adding a second five-wicket bag to his collection.
For a bowler accustomed to playing a support role, or toiling into the wind on his beloved Basin Reserve, four for 35 from 15 overs was a regretfully appropriate return.
"I was pretty keen to get five and make it part of my last test but it's probably pretty fitting I didn't as well," he said.
"I haven't had too many fives, so it's probably best I didn't in terms of the kind of player I am and the role that I've played."
He still described his spell as one of the most satisfying on his career, on a par with a hostile cameo in last week's second test in Wellington after New Zealand were rolled for 99.
"That was right up there in quality also," said O'Brien, whose 6-75 against the West Indies a year ago remains his best return.
Missing a five-wicket bag was not the only setback for the 33-year-old today - he revealed visa issues may delay his departure for England by several months, jeopardising his plan to join wife Rosie by Christmas.
Asked if that meant be would be available to play against Bangladesh in February and possibly Australia, O'Brien replied: "It's already been asked and it's already been answered: `No'.
Meanwhile, Imran Farhat, Pakistan's star performer on day one was understandably delighted to contribute 117 of Pakistan's wonky first innings tally of 223.
The 27-year carried his bat throughout the innings, becoming the fourth Pakistani to do so.
Farhat, playing his 30th test, had not made a test century since 2004 against India in Lahore - this series is his first after almost three years on the outer.
"I'm happy to be back after three years. The management has shown confidence in me, they have worked hard with me," he said after facing 169 balls.
He witnessed O'Brien's carnage from the non-striker's end, labelling his eight over spell before lunch as `fantastic'.
"It was not poor shot selection,
O'Brien's spell was fantastic. I just tried to stay on the pitch."
"The ball swings and seams, everything's happening here, you have to be patient."
