Over his professional career spanning nine years in Hungary's NB1 league, he contributed his skills to prominent clubs such as Újpest FC, REAC, and Nyíregyháza Spartacus.

This success repeated in the 2005/2006 season, where Illyés contributed to Újpest's second-place finish in a memorable match at the Puskás Ferenc Stadium, narrowly missing the NB1 championship title.

Moving to the United States in February 2012, Illyés joined the Atlanta Silverbacks, participating in the North American Soccer League and he was the number one goalkeeper during the 2012 NASL season.

In the autumn of 2009, Illyés Dániel commenced his role as a goalkeeper coach within the youth development program of REAC while being an active player for the club.

The Egri Kapus Akadémia came into fruition in the spring of 2010, its legal framework supported by the Fiatal Labdarúgó Kapusokért Alapítvány (Young Football Goalkeepers Foundation).

The success of the goalkeeper academy was particularly evident in its summer camps, which, between 2010 and 2019, became some of the largest in the country, drawing participants from various regions, both nationally and internationally.

In collaboration with Illyés, Stewart facilitated unique opportunities for talented goalkeepers to partake in training sessions at renowned English clubs such as Bolton, Everton, and Manchester City.