Cullen will join the Celtic League champions as soon as Wellington's provincial campaign is finished, but, with one match to play in the round-robin stage, the Lions are in the box seat for a semi-final spot.
Despite the heavy home loss on Friday night, Wellington are lying fifth in the table - only four points behind leaders Otago. And their final match this coming weekend is against Northland, who have failed to win a match all season.
A win will guarantee Wellington a spot in the semis - and delay Cullen's move by at least a week. A win in that semi-final will see the Lions in the NPC final on the weekend of October 24-26, with New Zealand's leading Test try-scorer flying to Ireland the following week.