But Rowntree, who was in a similar position when he was selected as scrum coach on the last Lions tour to South Africa three years ago, believes his countryman has everything it takes to succeed with Britain and Ireland's elite.
"I love working with the bloke," said Rowntree, when asked why Farrell was the right man for the job.
"He brings an unrivalled energy and passion to his work, on and off the field. The lads quickly buy into that. You can see it in their faces in meetings when he presents and when he shows his clips, he's just so positive.
"But he's honest as well. He's not a flowery coach. He doesn't beat around the bush. He's very energetic and that passion comes through in his players. I think you've seen that in the way our guys have performed with England."
And if Rowntree had to highlight one area of Farrell's coaching make up that could be crucial when the Lions head Down Under, it would be his positivity, something that he hopes will shine through during both the ups and downs of a six or seven-week tour.
"He's ultimately positive in every facet," added Rowntree.
"Even when he's debriefing a loss, he'll pull out the positives first and we'll build on those positives.
"He's been a tremendous addition to our England coaching team and I'm delighted for him that this has happened to him quite early in his coaching career - certainly early in his international career.
"He fully merits it and I'm looking forward to working with him for the Lions."