The 27-year-old has been snapped up by owners Middleham Park Racing to partner the Richard Hannon-trained son of High Chaparral, who is a general 14-1 chance to land the world's oldest Classic.
Few jockeys have a better big-race record on Town Moor than the Newmarket-based Italian, who struck aboard the Roger Varian-trained Kingston Hill in 2014 and followed up 12 months later with Simple Verse for Ralph Beckett.
Atzeni, who also won the Racing Post Trophy four years in succession from 2013 to 2016, told Press Association Sport: "I'm glad to get the ride on him. Jamie Spencer was meant to ride him, but I don't think he is at Doncaster.
"He is 100 per cent an ideal Leger type and that is why they are running him in it. Kew Gardens looks the one to beat, and Lah Ti Dar will be hard to beat if she turns up, but he has done nothing wrong all season.
"It is not like he is a 50-1 shot, he goes there with a chance. I'm lucky to get the ride on him and I'm looking forward to it. I've never ridden him before, but I've seen plenty of him. The trip will not be a problem.
"He does need to relax as Doncaster is a long, galloping, fair track and it is important for horses to relax."
On his affinity with the South Yorkshire circuit, Atzeni added: "It is just one of those things.
"I'm usually away for the Lincoln and November Handicap, but I've been very lucky to ride some good horses in the St Leger, Racing Post Trophy and Doncaster Cup."
As for Marlborough handler Hannon, he believes Atzeni is an ideal partner for his dual winner, who finished second in the Geoffrey Stakes at Newbury on his most recent start.
Hannon said: "We've got Andrea Atzeni for the Leger, which will suit him. He is a very good jockey around there.
"Hopefully he will get him to settle, let him drop his head and get him relaxed through the race to allow him every chance of getting the trip."
