The six-year-old – with Hugh Bowman aboard – looked like he'd win comfortably after finding the front before the 200m mark.
But Mazu showed his class for Peter and Paul Snowden, the four-year-old and fellow Everest contender never giving up on the inside.
2022 Premiere Stakes Replay
“It was a super win because Hugh had to get off the back of Overpass who took him nowhere,” O'Shea said.
“So he had to make a really long run on him. But that is the way you want to ride a 6/4 chance, take all the luck out of it.”
O'Shea believes Lost And Running is ready to improve on the fourth he got in last year's Everest.
“He's going to come on so much for that,” he said.
“He was probably on empty with 100m to go, but he got the job done and we can go to the big race in a couple of weeks with our tail in the air and hopefully get another win.
“He will come on for that. It is a great result for the stable, the owners, and everyone involved.”
Bowman echoed those thoughts.
“He's really on track and he's got the benefit of having been through the series last year, and improved every race and ultimately ran fourth in the main event,” he said.
“But this year things are going a lot better for him and he's a more mature individual. He's certainly on track.”