Filling in for Tommy Stinson, who is touring with his reunited group The Replacements, the bassist played the first of five shows with the band at Estadio Ferrocarril Oeste.
Introducing his old bandmate to the crowd, Rose said, "Our regular bass player, Mr. Tommy Stinson, is doing a show at Coachella with The Replacements, so we had to try to find a new guy. He's hanging in there. Please give a hearty welcome to the new guy, Mr. Duff MCKagan."
MCKagan, who quit the band in 1997, will join Axl Rose and the group onstage again in Asuncion, Paraguay on 9 April (14). 9, La Paz, Bolivia on 12 April, Recife, Brazil on 15 April and Fortaleza, Brazil on 17 April.