In 1991-92, Rhett Warrener played his first two major junior games with the WHL's Saskatoon Blades. The following season, he joined the Blades full time and scored 19 points as a WHL rookie. In 1993-94, Warrener scored 26 points in 61 games; in 1994-95, he scored 13 goals and 39 points in 66 points. In 1995-96, he played nine games for the AHL's Carolina Monarchs.
The Florida Panthers selected Warrener in the 2nd round, 27th overall, in the 1994 NHL Entry Draft. He went on to appear in 28 games that rookie season as the Panthers made the playoffs for the first time in franchise history. In the post-season, he helped the Panthers win the Prince of Wales Trophy in the Eastern Conference finals before losing to the Colorado Avalanche in the Stanley Cup final. During the 1998-99 season, Warrener was traded to the Buffalo Sabres. Upon his arrival with the Sabres, Warrener was a key player in the club's playoff run, he helped the Sabres win the Prince of Wales Trophy in the Eastern Conference finals before losing to the Dallas Stars in the Stanley Cup finals.
The Shaunavan, Saskatchewan native posted a career high 19 points in 2000-01 and continued to play a strong game until injuries limited him to 65 games in 2001-02 and 50 games the following year. In the summer of 2003, Warrener was acquired by the Calgary Flames and was for the third time in his career was a Stanley Cup finalist, as the Flames fell to the Tampa Bay Lightning in a hard-fought seven game series.
On the international stage, Warrener won a bronze medal with Canada's under-18 junior team at the 1993 Pacific Cup and then won a gold medal with Canada at the 1996 World Junior Championships.