"Our boys were shattered and [Nelson's] depth with the guys they brought on meant they got away on us in the last quarter of an hour."
Collegiate's next game will be against Canterbury's Christ's College on Wednesday, who were beaten in their opening game by Wellington College.
Lennox said it was ominous as Wellington has a very large and physical forward pack.
Kickoff on Saturday is around 11am.
Back home, Wanganui High School 1st XV had their blood up after upsetting Collegiate last Wednesday and poor City College were left to bare the brunt on Saturday.
WHS thumped them 80-0 for the start of the co-ed cup competition.
Coach Darryl Malcolm said he was able to give his full squad a run in the one-way traffic.
The team is still without regular captain Scott Bowater, while they have picked up a couple more injuries to work through before playing Tu Toa Academy at home.