Senior began his career at the Sheffield Eagles. He was signed from Huddersfield YMCA rugby union team by Gary Hetherington in 1995. Senior played in the very first Super League match in 1996, a 30-24 defeat to Paris Saint-Germain. He was also his club’s top try scorer with 17 tries that season. He bettered that tally in 1998, when he scored 19 tries as the Eagles shocked the rugby league world, beating the Wigan Warriors 17-8 in the Challenge Cup final at the old Wembley Stadium.
Senior made 139 appearances for the Eagles and scored 55 tries during his five seasons at the club. Notably, two of those tries came against his future employer, the Leeds Rhinos.
Senior signed for the Rhinos on the final day of the 1999 Super League regular season. He made his debut for the club on the same day, against the London Broncos. After a quiet start to his Rhinos career, Senior burst into life in 2000 finishing the season as joint top try scorer with 18, including four in a single match against the then Halifax Blue Sox.
Senior also represented Yorkshire in the now defunct ‘War of the Roses’ Origin Series, against cross-Pennine rivals Lancashire. Senior played in three consecutive defeats in 2001 and 2002, twice at Headingley, scoring two tries. In 2003 Yorkshire beat Lancashire. Senior scored two tries in the 56-6 victory at Odsal Stadium. In 2003 Senior was named the Leeds Rhinos Players’ Player of the Year.
In 2004 Senior made 30 appearances and scored 13 tries as the Rhinos ended their 32-year wait for the Championship, beating the Bradford Bulls 16-8 in the 2004 Super League Grand Final. By this time Senior held the record of playing the most Super League rounds of any player, with 223 out of a possible 237.
As Super League IX champions, the Rhinos faced 2004 NRL season premiers, the Bulldogs in the 2005 World Club Challenge. Senior played at centre in Leeds’ 39-32 victory. In 2005 Senior became only the 20th player in the club’s history to score 100 tries in his career. Senior played for Leeds in the 2005 Challenge Cup final at centre in their loss against Hull FC. In January 2007 Senior celebrated his Testimonial match for the Rhinos with a 50-0 thrashing of his home town club, the Huddersfield Giants. Senior scored a late try in the match.
Senior was an integral part of the Rhinos squad that won the Super League Grand Final for three consecutive seasons in 2007, 2008 and 2009, all against St Helens. During the 2009 season, Senior became the first player to reach 500 Super League appearances.
In 2009 Arriva Yorkshire asked local members of the public to nominate the thirteen best ever rugby league players to have played in West Yorkshire as the ‘Arriva Yorkshire Rugby League Dream Team’.
Senior made the final thirteen, along with rugby league greats Trevor Foster MBE, Neil Fox MBE, Albert Goldthorpe, Alan Hardisty, Lewis Jones, Stan Kielty, Roger Millward MBE, Malcolm Reilly, Garry Schofield, David Topliss, Dave Valentine, and Adrian Vowles.
A ceremony was held in August 2009 at The Jungle, the home of the Castleford Tigers. A fleet of new buses were named after all the players. He also announced his retirement from representative rugby in 2009. At the end of the 2010 season Senior was named in the Super League Dream Team for the fifth time in his career.
“Keith is a true war horse, a world class player, it is an honour to have worked with such a great champion”
Warrington and former Leeds Rhinos/Great Britain coach Tony Smith
“Internationally, in the modern era he has been one of the few backs who has regularly troubled the Aussies. He has been a credit to himself.”
Leeds Rhinos president Harry Jepson
“For any supporter, the sight of Senior, with ball in hand, his long stride tormenting the opposition defence, is one of rugby leagues most exciting images.”
Golf Superstar Lee Westwood
“As a player, I think Keith is up there with the very best of the modern era. His longevity alone marks him out as someone special.”
Leeds Rhinos captain Kevin Sinfield.