Shields made his senior League of Ireland debut with the first team in the final game of the 2008 season in a 2-0 defeat away to Sligo Rovers.

[2] Shields left Bray at the end of the 2011 campaign and was a free agent training with Leinster Senior League side Booth Road Celtic F.C.

There was a massive improvement in the 2013 Premier Division, with Dundalk finishing in second place, three points behind winners St. Pat's, and they also reached the semi-final of the FAI Cup.

He was part of the group that made history in Europe in 2016, although they suffered disappointment the following year as Cork City won both the league and FAI Cup.

In 2018, Shields enjoyed the best season of his career and scored the decisive goal in their top of the table clash with Cork that helped them secure a fourth league win in the space of five years.