India suffered a 1-2 defeat at the hands of defending champions New Zealand in their round-robin league encounter, where a victory would have secured them a spot in the title encounter against top-placed Australia.
"I'm obviously disappointed with the loss. We had our chances that we could not convert," Oltmans said.
"The hot and humid conditions took a lot out of the boys and we were not able to get the energy we had shown in our earlier matches," said Oltmans, who praised the rivals for overcoming the conditions better.
The mercury in Ipoh had crossed 37 degrees Celsius, and it was much hotter on the pitch with the heat from the watered turf making the players' task tougher.
"The execution of penalty corners suffered because of the humid conditions. The slippery hands were not able to perform the perfect job," Oltmans said about the two penalty corners in the second half when India went about looking for the equaliser.
An Indian victory today would have secured their position among the top two countries in the round-robin league that will play-off for the title on Saturday.
New Zealand now have 11 points from their six matches and now await the result of India's last fixture against Malaysia on Friday. If India win that match, they will play in the final on Saturday.
New Zealand's coach Colin Batch said his players showed good signs and the reward was a victory over India.
"I am told that yesterday was hot, and today was hotter. The players only get some relief when the sun goes behind the clouds," said Batch. "Both teams deserve full credit to be able to play a good game."
Batch said his players now get two days to recover from the effects of the stamina-sapping conditions before the medal play-offs on Sunday.
"Whether we play in the final or not is out of our hands. We will closely observe the results on Friday," he said.
New Zealand rode on goals form Ken Russell (28th minute) and Nick Wilson (41st) to overcome India, for whom the lone goal came from Mandeep Singh (36th).
