[12] He and Mustaine teamed up one final time in 2004 to record Megadeth's comeback album, The System Has Failed, though Poland opted not to rejoin the band full-time.

[12] In 2009, Poland formed OHMphrey, a side-project with Robby Pagliari of OHM, and Jake Cinninger, Kris Myers, and Joel Cummins of progressive rock band Umphrey's McGee.

[14] In 2019, Poland appeared on the track "Hammer (Comes Down)", on Megadeth bassist David Ellefson's solo release Sleeping Giants, with Mark Tremonti, Thom Hazaert, Dave McClain and Joey Radziwill of Sacred Reich, and Flotsam and Jetsam vocalist Eric AK.

[15] It was later announced Poland had signed to Ellefson's revived Combat Records, who would release a 30th Anniversary Edition of his solo debut Return to Metalopolis in 2020.

[16][17] In January 2020, Poland was inducted into the Metal Hall of Fame, alongside Geoff Tate, Don Dokken, Joe Satriani, Steve Vai, Prong, Graham Bonnet, and more.

Poland was inducted by Hazaert and former Machine Head guitarist Phil Demmel who joined Poland for a performance of "Peace Sells", with Butcher Babies bassist Ricky Bonazza, and Dead by Wednesday drummer Opus Lawrence and guitarist Dave Sharpe, who also tour with Ellefson and Hazaert in Ellefson's "Sleeping Giants" solo band.