New Zealand lost each of their top six batsmen to a spinner in Thursday's win against Bangladesh before pulling off a tight chase for their second victory of the tournament.
Bangladesh's spinners sent down 28 of the 47 overs in the innings, a prospect Stead's side might face again against a spin-heavy Afghanistan.
"Afghanistan are definitely a force and spin is one of their strength areas," Stead said on Friday.
"We expect that against some of the Asian sides in particular. We have played spin well in the past and maybe the pressure of the moment the other night made for some poor decisions."
Afghanistan strike largely through leg-spinner Rashid Khan and the off-spin duo of Mujeeb Ur Rahman and Mohammad Nabi who collectively bowled the bulk of the overs in their defeat by Sri Lanka on Tuesday.
"We’ve certainly done homework on Rashid, Mujeeb and Nabi – the likes of those guys who will definitely be a force for Afghanistan," Stead said.
"We’re also expecting a wicket with good pace in it at Taunton. It does spin for four-day games here but for the World Cup it’s well-grassed, so should have some good pace."
Afghanistan skipper Gulbadin Naib earlier predicted his counterpart Kane Williamson will struggle to read Rashid even after two seasons of sharing a dressing room with the spinner at Sunrisers Hyderabad in the Indian Premier League.
"I think it's not only for Kane, also it is difficult for our players too. It's difficult for our batsmen and we're playing against him in the nets," he told reporters.
Though not a great turner of the ball, Rashid's guile and accuracy make him a limited-overs asset especially sought after by Twenty20 franchises across the cricketing world.
The 20-year-old bowls a mean googly but it is his ability to bowl quickly through the air that hurries the batsmen.
"He is very different, quick and fast. He doesn't give you time to pick him. So it's very difficult," Naib added.
Afghanistan batsmen will have their own challenges against a formidable New Zealand pace attack including Matt Henry, who leads the tournament's wicket-takers' list, and Trent Boult, the number two-ranked ODI bowler.
Naib said they would try to play the "Afghan way" to bounce back from losses in their first two matches when they face the 2015 finalists.
"We will play our natural game, just go for who we are and why we're here," he said.
"It's important we don't look for the names (in the New Zealand team), just play the ball.
"They have plenty of experience in the New Zealand side – Trent Boult and other guys. But we look forward to playing our natural game and playing the Afghan way. Hopefully we do the best we can."
(Reporting by Amlan Chakraborty in London; editing by Christian Radnedge and Toby Davis)
