South Africa were clinical in victories over Sri Lanka and Australia in their first two games, but sloppy and careless in what proved a well-deserved victory for the Dutch in Dharamasala.
"We need to have some conversations with the boys," Bavuma said after a defeat in which his bowlers conceded 32 extras, the second-highest ‘scorer’ in the Netherlands innings.
"The extras, that's something you can control. Getting 30 (32) extras, that is an extra five overs and is always going to hurt you.
"That is a conversation for us to have – whether it is skill or a complacency thing – but in the end it did count for quite a lot."
South Africa had the Netherlands reeling at 112 for six after sending them in to bat, but bowled far too short and allowed the Dutch to reach 245 in their 43 overs in a game shortened due to rain.
"We definitely dropped the ball there letting them get to 240-plus," Bavuma said.
"With the batting, we were still confident in chasing down that score but we didn't get any partnerships. Their double-spin in the powerplay was something we did not adapt to.
"We were clinical against Australia, but the challenge was always to come back and replicate that performance. The fielding wasn't up to standard.
"The guys need to answer the questions themselves about where they were mentally. That's definitely not the standard we'd like to show from a fielding point of view."
South Africa next meet England in Wankhede on Saturday with their opponents also having lost their last outing, to Afghanistan, in what will be a big early match-up in the race for a semi-final place.
"Our campaign is not over by any stretch of the imagination, but you've got to feel the emotion of today and come back tomorrow with the head held up," Bavuma said.
