Rhyno

Following the closure of ECW, Gerin signed a contract with the World Wrestling Federation. He debuted on the March 19, 2001 episode of Raw under the ring name Rhyno as a heel, aligning himself with Edge and Christian. Rhyno went on to help Edge and Christian defeat The Hardy Boyz and The Dudley Boyz for the WWF Tag Team Championship in a Tables, Ladders, and Chairs match at WrestleMania X-Seven.
Rhyno, Edge, and Christian went on to form a stable with Kurt Angle known as Team RECK, with all four members reaching the semi-finals of the King of the Ring. Rhyno was eliminated from the event by the eventual winner, Edge. He went on to compete for the Hardcore Championship, which he won on three occasions in mid-2001.
On the July 9 episode of Raw, Rhyno joined "Team ECW". The stable, led by former ECW owner Paul Heyman, went on to merge with a rival stable of WCW alumni later that night, forming The Alliance. As a member of The Alliance, Rhyno feuded with Chris Jericho (who had insulted Stephanie McMahon, the on-screen owner of ECW, on numerous occasions).
On September 23 at Unforgiven, he defeated Tajiri for the WCW United States Championship. He held the title for just under a month before losing to Kurt Angle on the October 22 episode of Raw.
As a result of his loss, Rhyno was "suspended" from The Alliance on the October 25 episode of SmackDown!. The suspension was an angle concocted to explain Rhyno's absence while he underwent cervical fusion surgery for two herniated discs in his neck. The surgery was performed on November 12, 2001.
Rhyno returned to WWE television thirteen months later on the February 27, 2003 episode of SmackDown!, aligning himself with Chris Benoit thus making him a fan favorite for the first time since joining WWE. Rhyno and Benoit went on to unsuccessfully challenge Team Angle for the WWE Tag Team Championship in a triple threat tag team match (also involving Los Guerreros) at WrestleMania XIX.
Rhyno and Benoit continued to team together until July 2003, until Rhyno turned heel when he turned on Benoit. Rhyno wrestled on SmackDown! throughout the remainder of 2003 and early 2004, attempting to win the United States Championship on several occasions.
In March 2004, Rhyno was drafted to the Raw brand in the 2004 WWE Draft Lottery. Later that night he faced Chris Benoit for the World Heavyweight Championship in a losing effort. In July he turned face again by first squashing then heel Lance Storm in a match and then forming a tag team with Tajiri. The duo challenged for the World Tag Team Championship on several occasions throughout 2004.
Rhyno was released from his WWE contract on April 9, 2005 due to a public argument with his wife that took place at the WrestleMania 21 afterparty. He made his final appearance on WWE television at the WWE-produced ECW reunion pay-per-view One Night Stand on June 12 competed in a match against Sabu. During the match, fans chanted, "you got fired!" chants at Rhyno.