Walters, an important part of Ireland's dogged side who won his 50th international cap during qualification, missed the final two games of the campaign with a knee injury.
The 34-year-old forward has only made only two substitute appearances for Burnley in the league since signing in the close season.
"We'll see what the next seven or eight days bring," O'Neill told the Football Association of Ireland in reference to Walters's fitness.
While captain Seamus Coleman remains a long-term absentee after breaking his leg on international duty in March, his Everton team mate James McCarthy - who made his first competitive start since February this week - returns to the squad.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Hull City midfielder David Meyler is suspended for the first leg in Copenhagen on Nov. 11 but was included and will be available for the return game at home on Nov. 14.
Ireland Squad
Goalkeepers: Darren Randolph, Keiren Westwood, Rob Elliot, Colin Doyle
Defenders: Cyrus Christie, Matt Doherty, Paul McShane, Richard Keogh, Shane Duffy, Ciaran Clark, John O'Shea, Kevin Long, Stephen Ward
Midfielders: Aiden McGeady, Daryl Horgan, Alan Browne, Glenn Whelan, Conor Hourihane, Harry Arter, James McCarthy, Robbie Brady, Jeff Hendrick, Eunan O'Kane, David Meyler, Wes Hoolahan, Callum O'Dowda, Jonny Hayes, James McClean
Forwards: Shane Long, Daryl Murphy, David McGoldrick, Sean Maguire, Scott Hogan, Aiden O'Brien
(Reporting by Padraic Halpin, editing by Ed Osmond)
