Club After much success at underage levels, including four successive under-21 championships, Fennelly quickly joined the Ballyhale Shamrocks senior team. Two years later he was deployed further out the field as Ballyhale faced
O'Loughlin Gaels in the senior decider. An impressive 1–22 to 2–11 victory gave Fennelly his first
championship medal. He later added a
Leinster medal to his collection when Ballyhale secured a comprehensive 1–20 to 1–8 defeat of
Birr to take the provincial title for the first time in seventeen years. On 17 March 2007 Ballyhale Shamrocks faced
Loughrea in the All-Ireland decider. On a day when
Henry Shefflin and
James "Cha" Fitzpatrick were held scoreless, the three Reid brothers contributed 3–7 from play. A 3–12 to 2–8 victory gave Fennelly an
All-Ireland Senior Club Hurling Championship medal. Fennelly added a second championship medal to his collection in 2007 following a 1–20 to 1–10 drubbing of
St. Martin's. Ballyhale Shamrocks made it three-in-a-row in 2008. A 2–11 to 0–12 defeat of
James Stephens gave Fennelly a third successive championship medal. He later won a second Leinster medal as the Shamrocks defeated reigning champions Birr by 2–13 to 1–11. Fennelly won a fourth successive championship medal in 2009, as Ballyhale claimed a record-equaling four-in-a-row following a 1–14 to 1–11 defeat of James Stephens once again. The subsequent provincial decider saw Ballyhale hit fifteen wides, however, Fennelly still collected a third Leinster medal following a 1–16 to 1–8 defeat of
Tullamore. On 17 March 2010 Ballyhale faced three-in-a-row
Portumna in a "dream" All-Ireland decider. The game failed to live up to the billing, however, 1–19 to 0–17 victory gave Fennelly a second All-Ireland medal. Five-in-a-row proved beyond Ballyhale Shamrocks, however, the team bounced back in 2012 having lost the championship decider the previous year. A far from vintage 0–16 to 0–12 defeat of
Dicksboro gave Fennelly a fifth championship medal. Fennelly won a sixth championship medal in 2014 as the Shamrocks claimed a 1–20 to 1–13 defeat of reigning champions
Clara. Fennelly later collected a fourth Leinster medal as veteran Henry Shefflin proved the difference in a 0–21 to 1–14 defeat of
Kilcormacv/Killoughey. On 17 March 2015 Ballyhale faced
Kilmallock in the All-Ireland decider. A complete mismatch saw Shamrocks win the game by 1–18 to 1–6, with Fennelly collecting a third All-Ireland medal.
Minor and under-21 Fennelly first played for
Kilkenny as a member of the minor team during the
2003 Leinster Championship. He made his first appearance for the team on 25 June 2003 when he lined out at midfield in a 4-12 to 0-11 defeat of
Dublin. Fennelly was retained at midfield when Kilkenny qualified to play
Offaly in the
Leinster final on 6 July 2003. He was held scoreless throughout the game but ended with a
winners' medal after an 0-18 to 0-13 victory. On 14 September 2003, Fennelly was again selected at midfield when Kilkenny faced
Galway in the
All-Ireland final. He was once again held scoreless but claimed an
All-Ireland medal following the 2-16 to 2-15 victory. Fennelly was just out of the minor grade when he was drafted onto the Kilkenny under-21 team before the
2004 Leinster Championship. He made his first appearance in the grade on 2 June 2004 in a 0-20 to 2-10 defeat of
Laois. On 14 July 2004, Fennelly won a
Leinster Championship medal after lining out at left corner-back in a 1-16 to 2-03 defeat of
Wexford in the final. He retained his position at left corner-back when Kilkenny qualified for the
All-Ireland final against
Tipperary. Fennelly ended the game with a
winners' medal following a 3-21 to 1-06 victory. It was Fennelly's first
All-Ireland medal. On 20 July 2005, Fennelly missed Kilkenny's 0-17 to 1-10 defeat of Dublin in the
Leinster final due to a hand injury. He was back on the starting fifteen for the
All-Ireland final against
Galway on 18 September 2005, however, Fennelly ended the game on the losing side after a 1-15 to 1-14 defeat. On 27 July 2006, Fennelly won a third successive Leinster Championship medal - his second on the field of play - after lining out at midfield in the 2-18 to 2-10 defeat of Dublin in the
final. On 10 September 2006, he was again selected at midfield when Kilkenny drew 2-14 apiece with
Tipperary in the
All-Ireland final. Fennelly retained the midfield berth for the replay on 16 September 2006 and collected a second
winners' medal after the 1-11 to 0-11 victory.
Senior Beginnings While still a member of the under-21 team, Fennelly was added to the Kilkenny senior panel in 2006. He made his debut during the
National Hurling League, and subsequently collected his first winners' medal following a 3–11 to 0–14 victory over
Limerick. On 2 July 2006 he made his senior championship debut in a facile 1–23 to 2–12 provincial final defeat of Wexford. It was his first
Leinster medal. Fennelly later shared in Kilkenny's
All-Ireland defeat of
Cork as a non-playing substitute. Fennelly collected a second Leinster medal in 2007, as Kilkenny asserted their provincial dominance and defeated Wexford by 2–24 to 1–12. On 2 September 2007 Kilkenny faced defeated Munster finalists and surprise All-Ireland semi-final winners Limerick in the championship decider. Kilkenny got off to a flying start with
Eddie Brennan and
Henry Shefflin scoring two goals within the first ten minutes to set the tone. Limerick launched a second-half comeback, however, "the Cats" were too powerful and cruised to a 2–19 to 1–15 victory. Fennelly, who started the game on the bench, came on to collect his first All-Ireland medal on the field of play.
On and off the team In 2008 Fennelly broke his wrist in a club game which ruled him out of the latter stages of the provincial championship. He was back as an unused substitute as Kilkenny later claimed a third successive All-Ireland title following a 3–30 to 1–13 defeat of
Waterford. Fennelly was appointed captain of the team in 2009, however, he found it difficult to claim a place on the starting fifteen. On 6 September Kilkenny were poised to become the second team ever in the history of hurling to win four successive All-Ireland championships when they faced
Tipperary in the decider. Fennelly, in spite of being captain, started the game on the bench before being introduced as a late substitute. For long periods Tipp looked the likely winners, however, late goals from Henry Shefflin and substitute
Martin Comerford finally killed off their efforts to secure a 2–22 to 0–23 victory. Fennelly had collected his second All-Ireland medal on the field of play, while he also had the honour of lifting the
Liam MacCarthy Cup. In 2010 Kilkenny defeated Galway in an eagerly-anticipated but ultimately disappointing provincial decider. A 1–19 to 1–12 victory gave Fennelly a third Leinster medal. The drive for a fifth successive All-Ireland crown reached a head on 5 September 2010, when Kilkenny faced Tipperary in the All-Ireland decider. "The Cats" lost talisman Henry Shefflin due to injury, while Tipperary's
Lar Corbett ran riot and scored a hat-trick of goals as Fennelly's side fell to a 4–17 to 1–18 defeat. In spite of this defeat, Fennelly later won his first
All-Star award.
Continued dominance Kilkenny's stranglehold in Leinster continued in 2011. A 4–17 to 1–15 defeat of Dublin gave "the Cats" a record-equalling seventh successive championship. It was Fennelly's fourth winners' medal overall. Kilkenny subsequently faced Tipperary in a record-breaking sixth successive All-Ireland decider on 4 September 2011. Goals by Fennelly and
Richie Hogan in either half gave Kilkenny, who many viewed as the underdogs going into the game, a 2–17 to 1–16 victory. It was Fennelly's third All-Ireland medal, while he later collected a second consecutive All-Star and two
Hurler of the Year accolades. 2012 began well for Fennelly when he collected a second league medal following a 3–21 to 0–16 demolition of old rivals Cork. Kilkenny were later shocked by Galway in the Leinster decider, losing by 2–21 to 2–11, however, both sides subsequently met in the All-Ireland decider on 9 September 2012. Kilkenny had led going into the final stretch, however,
Joe Canning struck a stoppage time equaliser to level the game at 2–13 to 0–19 and send the final to a replay for the first time since 1959. The replay took place three weeks later on 30 September 2012. Galway stunned the reigning champions with two first-half goals, however, Kilkenny's championship debutant
Walter Walsh gave a man of the match performance, claiming a 1–3 haul. The 3–22 to 3–11 Kilkenny victory gave Fennelly a fourth All-Ireland medal. Kilkenny's dominance showed no sign of abating in 2013, Fennelly winning a third National League medal following a 2–17 to 0–20 defeat of Tipperary in the decider. In 2014 Fennelly collected his fourth league medal, as Kilkenny secured a narrow one-point 2–25 to 1–27 extra-time victory over Tipperary. He missed much of the provincial campaign but was restored to the starting fifteen on 7 September 2014 when Kilkenny faced Tipperary in the All-Ireland decider. In what some consider to be the greatest game of all-time, the sides were level when Tipperary were awarded a controversial free.
John O'Dwyer had the chance to win the game, however, his late free drifted wide resulting in a draw. The replay on 27 September 2014 was also a close affair. Goals from brothers
Richie and
John Power inspired Kilkenny to a 2–17 to 2–14 victory. It was Fennelly's fifth All-Ireland medal. An ongoing back injury hindered Fennelly's championship campaign in 2015, resulting in him missing Kilkenny's 1-25 to 2-15 defeat of Galway in the provincial decider. Fennelly fought his way back to full fitness as Kilkenny subsequently renewed their rivalry with Galway in the All-Ireland decider on 6 September 2015. The team struggled in the first half, however, a
T. J. Reid goal and a dominant second half display, which limited Galway to just 1-4, saw Kilkenny power to a 1-22 to 1-18 victory. The victory gave Fennelly a sixth All-Ireland medal while he was also chosen as the
man of the match. On 13 August 2016, it was confirmed that Fennelly would miss the
2016 All-Ireland final after he ruptured his achilles tendon in the semi-final replay victory over
Waterford. In December 2017, Fennelly confirmed his retirement from Inter-County hurling. His last game was the
2017 qualifier defeat to
Waterford on 8 July 2017
Inter-provincial After a two-year hiatus and a period of uncertainty surrounding the competition, the
Railway Cup returned in 2012 with Fennelly starting at midfield as
Leinster faced
Connacht in the decider. The game was effectively over at half time, with Leinster powering to an eventual 2–19 to 1–15 victory. ==Managerial career==