They were assisted in this by the constant errors from the home side - whether it was not finding touch, kicking too far, overthrowing a lineout or simply missing tackles, the Crusaders opened the door and the Rebels nearly ripped it off its hinges.
O'Connor, dangerous throughout, scored the try after the break to give the Rebels a real sniff of victory with a try to narrow the score to 21-19 and a well-worked front of a lineout move put hooker Ged Robinson in only moments later. It was superbly converted from the sideline by O'Connor for a 26-21 lead.
Dan Carter, playing his first match for a month after his paternity leave and hamstring injury, steadied the ship a little, but it was the goalkicking of Tom Taylor which proved most valuable.
Taylor kicked a difficult penalty into the wind to narrow the gap and added another shortly after to re-take the lead. Another three-pointer from in front with a few minutes to go eased the Crusaders out a little, but anxious moments remained for the home side.
The start could hardly have been better for the Crusaders, who scored through Guildford after a little over two minutes. It was an extraordinary beginning to the match - the Rebels held the ball from the kick-off and patiently built phase after phase until spilling it and allowing the Crusaders to launch a long-range counterattack. It was Guildford's first try of the season.
Another try followed less than 10 minutes later, first-five Tyler Bleyendaal going over after an attacking scrum.
It suggested a long and arduous afternoon was in store for the Rebels but they hit back with a Scott Higginbotham try.
However, as the Chiefs proved in Hamilton last night, sometimes a good start can backfire and so it proved with the Crusaders.
O'Connor's magic meant it was game on until some desperation at last from the Crusaders' forwards and Taylor's intervention.
Crusaders 30 (Zac Guildford, Tyler Bleyendaal tries; Tom Taylor con, 5 pens). Rebels 26 (Scott Higginbotham, James O'Connor, Ged Robinson tries; O'Connor con, 3 pens)
HT: 18-11