Stone Sour is an American rock band formed in Des Moines, Iowa, in 1992, performing for five years, before disbanding in 1997. They reunited in 2000 and since 2006, the group has consisted of Corey Taylor (lead vocals, guitar), Josh Rand (guitar) and Roy Mayorga (drums). Longtime members Joel Ekman (drums, percussion), Shawn Economaki (bass guitar), and Jim Root (guitar) left the group in 2006, 2011, and 2014 respectively. To date, Stone Sour have released six studio albums Stone Sour (2002); Come What(ever)

The band's third album Audio Secrecy, was recorded at the Blackbird Studios in Nashville, Tennessee with producer Nick Raskulinecz, who was the producer for the band's second album Come What(ever) May. and released on September 7, 2010 . Taylor stated that "Audio Secrecy is the summation of everything we want, everything we crave and everything we fight for...The dimensions go further than anything we've ever tried before. It's metal, rock, slow, soft, hard, fast, bitter, beautiful and most importantly, it's real. You can't get an album like this out of a band that doesn't exist. We're throwing caution out the damn window."  Stone Sour played the first annual Rockstar Energy Drink Uproar Festival with Avenged Sevenfold and Hollywood Undead among others. Stone Sour set the release date of Audio Secrecy as September 7. Stone Sour were part of the Soundwave Festival in late February/early March in Australia 2011. Stone Sour headlined The Avalanche Tour, supported by Theory of a Deadman, Skillet, Halestorm and Art of Dying. It was also announced that a Stone Sour live DVD will be released, filmed at the Brighton Centre in the United Kingdom. The band toured with Avenged Sevenfold, New Medicine and Hollywood Undead on the "Nightmare After Christmas Tour" 2011.  On April 16, 2011, it was announced that bassist Shawn Economaki had left the tour for personal reasons. Jason Christopher, who had played with Corey Taylor previously during his solo performances and with the Junk Beer Kidnap Band, filled in for the tour. In May 2011, Stone Sour canceled the remaining dates from their headline tour as drummer, Roy Mayorga suffered a minor stroke. He made a full recovery. The band played their last show of 2011 at the second day of the Rock in Rio IV festival, which took place in Rio de Janeiro, Brazil, between September 23 - October 2. Drummer Roy Mayorga was not present at the show as he was expecting his first child back home, and filling-in for him was ex-Dream Theater and The Winery Dogs drummer Mike Portnoy. Bassist Shawn Economaki was also absent from the performance.

Using a quote from the above article, answer the following question: Who replaced them?
filling-in for him was ex-Dream Theater and The Winery Dogs drummer Mike Portnoy.