Irish province Leinster will look to go one better in Saturday's final in London against Toulouse after losing the last two Champions Cup finals to another French club in La Rochelle, including an extraordinary match in Dublin last season when they were beaten after surging into an early 17-point lead.
Nienaber joined Leo Cullen's backroom staff at Leinster after masterminding a remarkable campaign in France last year where the Springboks won all three knockout games by just a point to retain the title they won at the 2019 World Cup in Japan.
"He's had a huge impact defensively, but in a lot of areas," Leinster lock Ryan told a pre-match press conference at the Tottenham Hotspur Stadium, the venue for the final, on Friday.
"With South Africa at the World Cup, you saw how close the games were; quarter, semi, final -- one-point games they were coming out on the right side and we were coming out the wrong side of games like that at Leinster."
The 27-year-old Ireland second row added: "So, being able to pick his brains on a week like this... unfortunately, like he said to us before, there is no magic pill.
"But it's about staying in the fight for the full 80 (minutes), making everything a contest; whether it's a ruck, a tackle or a barge; whatever it is, that's the way he looks at it."
Turning to Nienaber's impact on Leinster, co-captain Ryan said: "As a coach he gives unbelievably good clarity. It's easy to get behind.
"We've loved it and he's a bit of a character as well. He's got a good way of delivering messages."
Ryan said the pain of their recent final defeats would fuel Leinster in their quest to equal Toulouse's record tally of five Champions Cup titles.
"You do use it as motivation," he said. "It hurts to lose big games and, so, I'd be lying if I said we don't use it.
"At the same time, Toulouse won't be shy of motivation because we've beaten them (in the semi-finals) in the last two years of this competition."
Ryan will be among Leinster's replacements on Saturday after returning from a bicep injury last week in the United Rugby Championship.
"I'm delighted to get back training and playing last week and to be involved this week is amazing," he said.
"My job is to deliver a performance off the bench tomorrow (Saturday) for the team and hopefully I can do that."
