The actor turned down the part of Dr. Derek Shepherd and tells Variety Patrick Dempsey was always destined to play the medic.
"This is what longevity, experience and recovery give you," the former drug abuser tells the outlet. "There are no accidents. Whatever decision you come to, if you come to it from the right place, it's never wrong."
"Me in that part isn't as interesting as Patrick in that part. If it'd been me they (fans) wouldn't have called me 'McDreamy'; they would have called me Rob Lowe. Had I done Grey's, I wouldn't have been in Parks and Recreation. That alone for me is enough."
In the interview, Lowe also got candid about his 30 year battle with sobriety, revealing cocaine was everywhere in Hollywood when he became a badly-behaved Brat Pack star.
"It was no different than craft services," he explains. "Where are the Red Vines, and where is the great Peruvian blow...? Cocaine was the thing that successful people did. There was always that wonderful moment when, as an active drug abuser, you'd go on the set and figure out which department was selling the coke."
He also opened up about kicking his habit, adding, "Nothing can make you get sober except you wanting to do it. The threat of losing a marriage, losing a job, incarceration - you name the threat, it will not be enough to do it. It's got to be in you."
"And the only way to stay in recovery is to be honest with yourself on a minute-by-minute basis. No secrets, no double life. And you have to get real."