"I had a fair lead on Phil Costley and it would have been a tragedy if I had gone all that way and not been able to finish," he added.
After running at a pace to see him finish in 2h 22m, Warrander eventually crossed the finish in Fanshawe St in 2h 24m 42s, five minutes slower than his winning time last year in the adidas-sponsored event.
Warrander hopes his heel injury will recover in time for him to compete for New Zealand in an international relay event in Chiba, Japan, next month.
Costley from Nelson also had trouble over the second half with stomach cramping but still held on for second in 2h 28m 18s, with Blair McWhirter of Christchurch taking third in 2h 33m 4s ahead of marathon rookie Aaron Jackson, who recorded 2h 35m 8s.
Costley shared the front running over the first 7km, but when Warrander applied the pressure just before 10km he settled back to run his own race.
"I had a time in mind and was just running to my splits. I heard that Dale was in trouble later but I was also just holding on. Dale is a class act and he showed that today," said Costley.
Lisa Robertson was outstanding in her debut over the 42.2km marathon distance, leading throughout to set a fresh course record of 2h 41m 56s. The 28-year-old jockey was raring to go from the start and cut out the first half in 1h 18m 20s, about 20 seconds faster than Danielle Ingram-Trevis ran to win the separate half marathon race.
"I was aiming for a sub two hours forty but I had shin problems and had to take a few weeks easy so I wasn't entirely up to my game today, so to get that time is amazing."
Robertson said that being an active jockey does help her running fitness.
"Working in the gallops is like doing your 800m reps in running and things like that."
Australian marathon champion Kirsten Molloy was second in 2h 48m 10s, five minutes slower than her time in the Melbourne Marathon three weeks ago.
"I just loved the run over the harbour bridge and the course was so pretty the whole way. I don't know anybody but around the course they were yelling out to me - it was really nice."
Last year's winner, Shireen Crumpton, of Dunedin, was third in 2h 56m 5s. Crumpton has been troubled with an injured Achilles tendon.
"It was pretty sore the whole way, so I'm just happy to be here," said Crumpton.
"At least I sneaked under the three-hour mark, I would have been really disappointed if I hadn't," she added.
Stephen Lett won the New Zealand half marathon title in a personal best 1h 7m 38s, nearly two minutes ahead of Scott Winton, with Stefan Smith third.
Ingram-Trevis recorded 1h 18m 36s for the women's title. Sally Gibbs was second in a New Zealand masters record for a 48-year-old of 1h 19m 48s. Gabrielle O'Rourke, of Wellington, was third in 1h 20m 23s.