After facing some heart-breaking one-point defeats in a number of championship deciders, Ballyboden St. Enda's reached the county final once again in 2007. A 2-13 to 1-5 trouncing of St. Vincent's gave Ballyboden their first ever championship. It was a first championship medal for Maguire. Ballyboden St. Enda's went on to dominate club hurling in Dublin for the rest of the decade. Subsequent county final defeats of Kilmacud Crokes, Craobh Chiaráin, St. Vincent's again and O'Toole's gave Ballyboden a record-equaling five championship titles in-a-row. Maguire played a key role in goal in all of these victories, including being named Dublin Hurler of the Year in 2010.
Maguire first came to prominence on the inter-county scene as goalkeeper on the Dublin minor hurling team in 2000. He spent two seasons with the minors and enjoyed little success, having ended up on the losing side to Offaly in the 2000 Leinster final.
After later joining the Dublin under-21 team, Maguire featured when the team lost back-to-back provincial deciders in 2002 and 2003.
Maguire was still a member of the Dublin under-21 team when he made his senior debut in a National Hurling League game against Kilkenny. He made his championship debut later that same year in a Leinster quarter-final against Westmeath.
His first few championship seasons saw Dublin face some narrow losses in the provincial series of games, however, in 2009 Maguire's side qualified for a first Leinster final in eighteen years. A 2-18 to 0-18 score line gave victory to Kilkenny.
After a disappointing championship in 2010, 'the Dubs' qualified for the National League final in 2011, their first decider in over seventy years. An epic 0-22 to 1-7 defeat of Kilkenny gave Maguire a coveted National League winners' medal. Both sides met again in the Leinster final that day, however, the result was reversed on this occasion. A 4-17 to 1-15 score line gave victory to 'the Cats'. In spite of this defeat Dublin remained in the championship and reached an All-Ireland semi-final against reigning All-Ireland champions Tipperary. Maguire's side gave Tipp an almighty scare, however, the champions narrowly won by 1-19 to 0-18. Maguire finished off the season by winning his very first All-Star award.