When Sir Mark Todd and Leonidas II entered the Rio Olympic showjumping ring, New Zealand's eventing team were on the cusp of a maiden gold medal.

Four dropped rails later and their Games dreams were shattered by a brutal denouement.

Like the pole vault's bar, athletics' hurdles or cricket's bails, eventing punishes its participants' flaws with broken barriers. Today was Todd's turn to endure rare professional pain.

After Christopher Burton rode Australia into bronze, New Zealand were left fourth, unable to add to the team silver of Barcelona or the bronzes of Seoul, Atlanta or London.

The result highlighted what a cauldron the Olympic arena can be. The ghosts of Andrew Nicholson's nine dropped rails on Spinning Rhombus in 1992 returned.

Todd's unfortunate ride incurred 16 penalty points which, when added to Jonelle Price's eight, took them out of medal contention by 3.5 penalty points - or less than one dropped rail.

New Zealand finished on 178.80, behind Australia (175.3), Germany (172.80) and winners France (169.00).

"What do you say," Todd lamented. "It's disappointing for me and the whole team. I feel more disappointed for the team who had put us in a position to win a medal and it was up to me to deliver.

"My horse is normally a good jumper but he went out and froze in the atmosphere. There was nothing much I could do, I tried to relax him and stay calm, but he kept putting his head up and hollowing his back. It was awful.

"After the first [dropped rail] I tried to keep him calm because normally he doesn't drop more than one. Then two and three went down. I couldn't believe it. I was fighting to get home."

As the shock registered, the 60-year-old double Olympic gold medallist acknowledged he had not experienced anything like it since making his Games debut at Los Angeles in 1984.

"Not of my personal doing. But winning another medal was really important. To have it slip away at the last minute was devastating."

The performance shadowed the fine effort of Clarke Johnstone on Balmoral Sensation who went clear in his debut Games and moved into fifth on the individual standings. He has an outside chance of a medal when the jumping concludes later this morning.