"It was not difficult for me at all," Selig said. "I spent many, many hours thinking about it, trying to be fair, trying to be logical and rational. I wouldn't second-guess a thing at all. I thought it was eminently fair."
There has been a backlash from Rodriguez's camp because of the harshness of the 211-game penalty, and Rodriguez has appealed. The New York Yankees slugger is playing while the appeal is being considered.
"I can't control what people are saying," Selig said. "I have a job to do, and that's protecting the integrity of the game and enforcing it, and that's what I'm going to do. The public role in this thing — it is what it is and I accept that. I have no concerns about it."
"There are times you'd like it not to be this, but that's just the way life works out," he added. "We made a commitment. I made a commitment to a lot of people ... that we would do everything we can to clean up this sport. We have and we will. To be where we are today I think is remarkable."
Selig was asked about Rodriguez's suspension this month while the commissioner was announcing a major expansion of video replay for next season on Thursday.
Rodriguez was one of 14 players suspended in the Biogenesis scandal and received the stiffest penalty. Rodriguez, suspended through the 2014 season, is the only one who is appealing.
Brewers outfielder Ryan Braun received a 65-game suspension while All-Stars Nelson Cruz, Jhonny Peralta and Everth Cabrera were among 12 banned for 50 games apiece on Aug. 5 when MLB disciplined them for their relationship to Biogenesis.
Biogenesis, the now-closed Florida anti-aging clinic, was accused of distributing banned performance-enhancing drugs.